EP1679752B1 - Leitfähiger dünnfilm und dünnfilmtransistor - Google Patents

Leitfähiger dünnfilm und dünnfilmtransistor Download PDF

Info

Publication number
EP1679752B1
EP1679752B1 EP04793157A EP04793157A EP1679752B1 EP 1679752 B1 EP1679752 B1 EP 1679752B1 EP 04793157 A EP04793157 A EP 04793157A EP 04793157 A EP04793157 A EP 04793157A EP 1679752 B1 EP1679752 B1 EP 1679752B1
Authority
EP
European Patent Office
Prior art keywords
thin film
liquid crystalline
compound
semiconductor layer
film transistor
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP04793157A
Other languages
English (en)
French (fr)
Japanese (ja)
Other versions
EP1679752A4 (de
EP1679752A1 (de
Inventor
Naohide Matsusjita Electric Indus. WAKITA
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Panasonic Corp
Original Assignee
Panasonic Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Panasonic Corp filed Critical Panasonic Corp
Publication of EP1679752A1 publication Critical patent/EP1679752A1/de
Publication of EP1679752A4 publication Critical patent/EP1679752A4/de
Application granted granted Critical
Publication of EP1679752B1 publication Critical patent/EP1679752B1/de
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/20—Carbon compounds, e.g. carbon nanotubes or fullerenes
    • H10K85/221—Carbon nanotubes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K10/00—Organic devices specially adapted for rectifying, amplifying, oscillating or switching; Organic capacitors or resistors having potential barriers
    • H10K10/40—Organic transistors
    • H10K10/46—Field-effect transistors, e.g. organic thin-film transistors [OTFT]
    • H10K10/462—Insulated gate field-effect transistors [IGFETs]
    • H10K10/464—Lateral top-gate IGFETs comprising only a single gate
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
    • H10K71/10—Deposition of organic active material
    • H10K71/191—Deposition of organic active material characterised by provisions for the orientation or alignment of the layer to be deposited
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/60—Organic compounds having low molecular weight
    • H10K85/615—Polycyclic condensed aromatic hydrocarbons, e.g. anthracene
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/60—Organic compounds having low molecular weight
    • H10K85/615—Polycyclic condensed aromatic hydrocarbons, e.g. anthracene
    • H10K85/623—Polycyclic condensed aromatic hydrocarbons, e.g. anthracene containing five rings, e.g. pentacene
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/60—Organic compounds having low molecular weight
    • H10K85/649—Aromatic compounds comprising a hetero atom
    • H10K85/655—Aromatic compounds comprising a hetero atom comprising only sulfur as heteroatom
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/60—Organic compounds having low molecular weight
    • H10K85/649—Aromatic compounds comprising a hetero atom
    • H10K85/657—Polycyclic condensed heteroaromatic hydrocarbons
    • H10K85/6572—Polycyclic condensed heteroaromatic hydrocarbons comprising only nitrogen in the heteroaromatic polycondensed ring system, e.g. phenanthroline or carbazole
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/731—Liquid crystalline materials

Definitions

  • the present invention relates to a conductive thin film formed by orienting nanotube or an organic semiconductor compound as well as a thin film transistor employing the same as a semiconductor layer.
  • a thin film transistor (TFT) for use in flat panel displays and the like has a structure wherein source and drain electrodes are disposed on one side of a semiconductor layer forming part of the thin film transistor and a gate electrode disposed on the other side of the semiconductor layer at a substantially central position relative to a channel.
  • a semiconductor layer of a thin film transistor having the above-described structure is formed by processing a semiconductor thin film formed on a substrate under precise control based on a thin film control process.
  • the semiconductor layer of the thin film transistor formed by the thin film control process calls for an excellent carrier mobility for a semiconductor device to be constructed.
  • conventional thin film transistors preferentially employ inorganic semiconductors having excellent levels of carrier mobility such as silicon and germanium as semiconductor materials forming such semiconductor layers.
  • Such an electronic functional organic material has a characteristic that it can be deposited at room temperature or at a temperature close to room temperature. Accordingly, use of such an electronic functional organic material makes it possible to form a conductor or semiconductor layer by a low-temperature process. For this reason, it is possible to form a conductor or semiconductor layer by the use of relatively inexpensive fabrication equipment adapted to the low-temperature process without the need to provide expensive fabrication equipment adapted to a high-temperature process that is needed when using an inorganic semiconductor. In brief, such a conductor or semiconductor layer can be formed inexpensively.
  • These electronic functional organic materials generally have flexibility. Accordingly, the use of such an electronic functional organic material for a conductor or semiconductor layer makes it possible to impart the layer with flexibility For this reason, if a conductor or semiconductor layer comprising an electronic functional organic material is formed on a flexible plastic substrate or resin film, it becomes possible to fabricate an electrode, thin film transistor or the like having flexibility easily. Use of such a flexible electrode, flexible thin film transistor or the like enables a sheet-like or paper-like display or electronic device or the like to be constructed easily.
  • Examples of known thin film transistors of the type using an electronic functional organic material in a semiconductor layer include one having a semiconductor layer comprising oligothiophene which is an organic semiconductor compound.
  • the semiconductor layer of this thin film transistor comprises an oligothiophene thin film formed by evaporating oligothiophene on a substrate or depositing oligothiophene on the substrate by coating the substrate with a solution of oligothiophene in an organic solvent.
  • the semiconductor layer of this known thin film transistor is formed by mere evaporation or deposition of oligothiophene without orientation or alignment, the thin film transistor has a far lower carrier mobility at channel than a thin film transistor using silicon or the like.
  • the carrier mobility of such a thin film transistor having a semiconductor layer formed by mere evaporation or deposition of oligothiophene is about 0.001 cm 2 /Vs for example (see patent document 1 for example).
  • such a conductor or semiconductor layer comprising an electronic functional organic material has a problem that the carrier mobility thereof is considerably lower than that of a layer comprising an inorganic semiconductor.
  • the carrier mobility of single-crystalline silicon is about 10 3 cm 2 /Vs, that of polycrystalline silicon about 10 2 cm 2 /Vs, and that of amorphous silicon about 1 cm 2 /Vs, whereas that of a layer comprising such an electronic functional organic material as oligothiophene is about 0.001 to about 0.01 cm 2 /Vs.
  • the carrier mobility of the conductor or semiconductor layer comprising an electronic functional organic material is considerably lower than that of the layer comprising an inorganic semiconductor because the conductor or semiconductor layer formed by mere evaporation or deposition of the electronic functional organic material has electronic functional organic material molecules therein with their axes positioned disorderly, which impedes smooth charge transfer between plural electronic functional organic material molecules, thus lowering the electric conductivity of the layer.
  • a thin film transistor has been reported in which a crystalline low-molecular electronic functional organic material comprising pentacene or the like is used as an electronic functional organic material to form a semiconductor layer in which the low-molecular electronic functional organic material is oriented and aligned by an evaporation technique (see non-patent document 1 for example).
  • pentacene which is an organic semiconductor material
  • pentacene is evaporated on a substrate to form the semiconductor layer of the thin film transistor.
  • This evaporation process causes pentacene molecules to be substantially aligned in the direction normal to the substrate thereby realizing a thin film phase having poor grain boundary. It has been reported that such a structure realized a thin film transistor having a semiconductor layer having a carrier mobility of about 0.6 cm 2 /Vs, which is a relatively high value among values of carrier mobility obtained from semiconductor layers formed by using electronic functional organic materials.
  • the semiconductor layer comprises a liquid crystalline phase of a polythiophene derivative in which such a liquid crystalline substituent group as phenylcyclohexane (PCH)-type substituent is introduced at the 2- or 3-position of thiophene.
  • PCH phenylcyclohexane
  • FIG. 19 is a sectional view schematically showing a sectional structure of the thin film transistor according to the aforementioned patent document 2.
  • the thin film transistor 100 includes an insulating substrate 101 formed with a gate electrode 103, and an organic semiconductor film 106 formed over the insulating substrate 101 with a gate insulator 102 intervening therebetween. Further, between the insulating substrate 101 and the organic semiconductor film 106 are formed a source electrode 104 and a drain electrode 105 in such a manner as to connect to the organic semiconductor film 106 directly.
  • the organic semiconductor film 106 is formed by a process including: polymerizing a PCH-type liquid crystal compound (PCH504) and thiophene by a catalytic polymerization method; dissolving the resulting polymer in a chloroform solvent to exhibit a liquid crystalline phase; and coating the upper sides of the gate insulator 102, source electrode 104 and drain electrode 105 with the resulting solution to a film thickness of 1 ⁇ m by a casting method.
  • the organic semiconductor film 106 extending over the source and drain electrodes 104 and 105 is subjected to a treatment for orientation control.
  • the liquid crystalline substituent group introduced in the organic semiconductor polymer forming the organic semiconductor film 106 can be oriented parallel with a rubbing direction.
  • the skeletal chains of the organic semiconductor polymer are aligned in a fixed direction relative to the liquid crystalline substituent group, or side chain. Stated otherwise, in the thin film transistor 100 the direction in which the skeletal chains of the organic semiconductor polymer are aligned is controlled by controlling the alignment direction of the liquid crystalline substituent groups by an orientation treatment.
  • nanotube having a nanostructure, particularly, carbon nanotube (CNT), which is an inorganic compound formed from carbon (C) as a semiconductor material for forming a conductor or semiconductor layer.
  • CNT carbon nanotube
  • nanotube NT
  • carbon nanotube CNT
  • a carbon nanotube has a very small diameter on a nanometer order and a length on a micrometer order and hence has a very high aspect ratio. Therefore, carbon nanotube is extremely close to an ideal one-dimensional system.
  • Such carbon nanotubes include a metallic carbon nanotube having a high electric conductivity and a semiconductive carbon nanotube having a band gap in inverse proportion to the diameter thereof, which are produced in accordance with the diameter and the helical degree which depend upon the symmetry of the molecular structure thereof.
  • carbon nanotube is synthesized as a carbon nanotube mixture comprising the metallic carbon nanotube and the semiconductive carbon nanotube in proportions of about 1:2 for example.
  • the metallic carbon nanotube has a high electric conductivity, it is possible to use the metallic carbon nanotube as a favorable wiring material or as a conductive member for use in devices of microstructure.
  • the semiconductive carbon nanotube it is required that the semiconductive carbon nanotube be used.
  • Such a thin film transistor having a semiconductor layer formed by using the semiconductive carbon nanotube can obtain a very high carrier mobility at channel of 1000 to 1500 cm 2 /Vs.
  • FIG. 18 is a sectional view schematically showing the construction of a thin film transistor having a semiconductor layer comprising carbon nanotubes.
  • a thin film transistor 200 as shown in FIG. 18 includes a 150nm-thick gate insulator 202 comprising thermally oxidized silicon formed on an upper portion of a p + silicon substrate 201 which serves also as a gate electrode, and a 1.4nm-thick semiconductor layer 203 formed by dispersing semiconductor-type carbon nanotubes of 1.4 nm diameter on the gate insulator 202 at an appropriate dispersion density.
  • a metal such as titanium (Ti) or cobalt (Co) is deposited on the surface of the semiconductor layer 203 by evaporation and, further, source electrode 204 and drain electrode 205 each comprising titanium carbide or cobalt are formed on upper sides of contact sections 206 and 207 in contact with the carbon nanotubes.
  • the thin film transistor 200 is thus constructed. Such a construction yields a nanotube-type thin film transistor having a sufficiently high carrier mobility at channel and favorable electrical characteristics.
  • the carrier mobility of the semiconductor layer is still lower than that of a semiconductor layer formed by using such an inorganic semiconductor as silicon due to the degree of orientation of the electronic functional organic material still remaining low, though the carrier mobility is somewhat improved as compared with a conventional semiconductor layer comprising the electronic functional organic material not oriented or aligned. That is, for the electronic functional organic material to be used in forming a semiconductor device, wiring or the like, it is required that the degree of orientation of the electronic functional organic material be further improved with the characteristics of the electronic functional organic material maintained to improve the flow characteristics of electrons or holes, thereby further improving the carrier mobility of the semiconductor layer or the electric conductivity of the conductor layer. In order to provide a conductor or semiconductor layer that can find applications in higher-performance and further miniaturized semiconductor devices which will be required in near future, the degree of orientation of the electronic functional organic material need be further improved to further enhance the carrier mobility.
  • pentacene which is a low-molecular organic semiconductor compound
  • pentacene is evaporated on the substrate so as to be oriented and aligned; however, it is actually difficult to obtain pentacene crystal extending over a large area.
  • a thin film transistor having a semiconductor layer comprising pentacene crystal close to single crystal formed on a flexible substrate involves a problem that the semiconductor layer may be damaged by some manner of handling of the thin film transistor, which may result in a defect in the semiconductor layer.
  • the liquid crystalline polymer in the formation of the semiconductor layer, the liquid crystalline polymer is used comprising a polythiophene derivative in which a liquid crystalline substituent group is introduced and the backbone chain of the polythiophene derivative is oriented by orientation of the liquid crystalline substituent group in the liquid crystalline phase.
  • the PCH-type liquid crystal compound which does not contribute to charge transfer, is chemically bonded as side chain to the polythiophene derivative having a low carrier mobility.
  • the proposition cannot exert any favorable influence from the view point of charge transfer and hence has a difficulty in sufficiently enhancing the carrier mobility at channel, though is capable of forming a semiconductor layer in which an electronic functional organic material is oriented by a simple and convenient method.
  • nanotubes having a high value of carrier mobility are used and dispersed at an appropriate dispersion density to form the semiconductor layer.
  • a semiconductor layer of a very small thin film transistor is to be formed, it is difficult to align and fix multiple nanotubes of nanostructure side by side without superposing them one upon another from the view point of fabrication process.
  • Such a conductor or semiconductor layer formed by dispersing nanotubes is poor in flex resistance. For this reason, it is difficult to form a conductor or semiconductor layer consisting only of nanotubes on such a flexible substrate as a plastic substrate. That is, such a structure makes it difficult to form a flexible electrode, a flexible thin film transistor or the like.
  • a conductor or semiconductor layer is formed by using a composite-type material comprising a mixture of high-mobility nanotube and a flexible organic compound, formation of an electrode or thin film transistor which has a high value of carrier mobility and is flexible is considered to become possible.
  • such a conductor or semiconductor layer comprising the aforementioned composite-type material
  • mere mixing of the organic compound and nanotube causes nanotube molecules of a substantially one-dimensional shape to be positioned sparsely in random orientations and hence cannot provide for a conductor or semiconductor layer of high carrier mobility.
  • such a conductor layer comprising the aforementioned composite-type material has a low electric conductivity of about 10 ⁇ -1 cm -1 .
  • the existing orientation treatment means has a difficulty in orienting nanotube satisfactorily.
  • the present invention has been made in view of the foregoing circumstances. Accordingly, it is an object of the present invention to provide an inexpensive and flexible conductive thin film which is excellent in carrier mobility and electric conductivity and which is formed by highly orienting nanotube or an electronic functional organic material by simple and convenient means, as well as a thin film transistor employing the same.
  • molecules of nanotube and organic compound having high carrier mobility or electric conductivity need be aligned densely and favorably at an improved degree of orientation in a predetermined direction by a simple method.
  • the present invention provides a conductive thin film formed by mixing a first material having electric conductivity or semiconductivity and a second material to prepare a mixture and orienting the mixture by utilizing liquid crystallinity thereof.
  • the conductive thin film is formed by mixing at least nanotubes comprising at least one of metallic nanotubes and semiconductive nanotubes and a liquid crystalline organic compound together and orienting molecules of the liquid crystalline organic compound to cause molecules of the nanotubes to be oriented.
  • the aforementioned nanotubes are carbon nanotubes.
  • the aforementioned liquid crystalline organic compound is a liquid crystalline organic compound having at least one of a nematic liquid crystalline phase and a smectic liquid crystalline phase.
  • the aforementioned liquid crystalline organic compound is a liquid crystalline organic compound having a charge transport function.
  • the aforementioned liquid crystalline organic compound is a liquid crystalline organic compound having at least any one of a 2-phenylnaphthalene ring, a biphenyl ring, a benzothiazole ring and a t-thiophene ring and a substantially rod-like molecular structure.
  • the method of fabricating a conductive thin film comprises: mixing at least nanotubes comprising at least one of metallic nanotubes and semiconductive nanotubes and a liquid crystalline organic compound having a charge transport function together; and orienting molecules of the liquid crystalline organic compound to cause molecules of the nanotubes to be oriented.
  • Carbon nanotubes are used as the aforementioned nanotubes.
  • a liquid crystalline organic compound having at least one of a nematic liquid crystalline phase and a smectic liquid crystalline phase is used as the aforementioned liquid crystalline organic compound.
  • a liquid crystalline organic compound having at least any one of a 2-phenylnaphthalene ring, a biphenyl ring, a benzothiazole ring and a t-thiophene ring and a substantially rod-like molecular structure is used as the aforementioned liquid crystalline organic compound.
  • the present invention also provides a thin film transistor comprising a conductive thin film as recited in claim 1 as a semiconductor layer forming a channel layer.
  • the aforementioned conductive thin film is a conductive thin film formed by mixing at least nanotubes comprising at least one of metallic nanotubes and semiconductive nanotubes and a liquid crystalline organic compound having a charge transport function together and orienting molecules of the liquid crystalline organic compound to cause molecules of the nanotubes to be oriented.
  • the present invention also provides a method of fabricating a thin film transistor, comprising a method of fabricating a conductive thin film as recited in any of claims 6 to 10 as a method of fabricating a conductive thin film serving as a semiconductor layer forming a channel layer.
  • the aforementioned method of fabricating a conductive thin film comprises the steps of: mixing at least nanotubes comprising at least one of metallic nanotubes and semiconductive nanotubes and a liquid crystalline organic compound having a charge transport function together; and orienting molecules of the liquid crystalline organic compound to cause molecules of the nanotube to be oriented.
  • the present invention also provides an image display device comprising a conductive thin film as recited in any of claims 1 to 5 as at least one of a conductive layer and a semiconductor layer forming a channel layer of a thin film transistor.
  • the aforementioned conductive thin film is a conductive thin film formed by mixing at least nanotubes comprising at least one of metallic nanotubes and semiconductive nanotubes and a liquid crystalline organic compound having a charge transport function together and orienting molecules of the liquid crystalline organic compound to cause molecules of the nanotubes to be oriented.
  • the present invention also provides an electronic device comprising a conductive thin film as recited in any of claims 1 to 5 as at least one of a conductive layer and a semiconductor layer forming a channel layer of a thin film transistor.
  • the aforementioned conductive thin film is a conductive thin film formed by mixing at least nanotubes comprising at least one of metallic nanotubes and semiconductive nanotubes and a liquid crystalline organic compound together and orienting molecules of the liquid crystalline organic compound to cause molecules of the nanotubes to be oriented.
  • the present invention which is practiced by the above-described solution means, is capable of providing an inexpensive and flexible conductive thin film having excellent carrier mobility and electric conductivity which is formed by highly orienting nanotube or an electronic functional organic material by simple and convenient means, as well as a thin film transistor employing such a conductive film.
  • the conductive thin film is formed by using the composite-type material comprising a mixture of nanotube and the liquid crystalline organic compound, since the nanotube is highly oriented by utilizing a high degree of orientation of the liquid crystalline organic compound, the conductive thin film having excellent carrier mobility and electric conductivity and the thin film transistor employing the conductive thin film can be fabricated by a simple and convenient method.
  • the conductive thin film is formed from the liquid crystalline electronic functional organic material comprising the non-liquid-crystalline electronic functional organic material and the non-liquid-crystalline organic compound which are hydrogen-bonded to each other, since the liquid crystalline electronic functional organic material is highly oriented by utilizing the conventional orientation technique, the conductive thin film having excellent carrier mobility and electric conductivity and the thin film transistor employing the conductive thin film can be fabricated by a simple and convenient method.
  • the non-liquid-crystalline organic compound can be removed by cutting off the hydrogen bond after having highly oriented the liquid crystalline electronic functional organic material, the conductive thin film exhibiting a sufficiently high carrier mobility which inherent to the electronic functional organic material and the thin film conductive film employing the conductive thin film can be fabricated by a simple and convenient method.
  • the conductive thin film is formed from the mixed composition comprising a mixture of the electronic functional organic material having the first liquid crystalline phase which has a high order at a high temperature or a potentially high order and the organic compound exhibiting the second liquid crystalline phase of a low order, since the second liquid crystalline phase of a low order is exhibited to cause the electronic functional organic material to be oriented in a predetermined direction, the conductive thin film having excellent carrier mobility and electric conductivity and the thin film transistor employing the conductive thin film can be fabricated by a simple and convenient method.
  • conductive thin film is meant to include both a thin film conductor to form an electrode, wiring or the like and a thin film semiconductor to form a thin film transistor or an organic electroluminescent device.
  • Embodiments 1 to 3 of the present invention to be described below are embodiments each realizing a conductive thin film which is further improved in electric conductivity and carrier mobility and which is formed by preparing a composite-type material by mixing carbon nanotube as a conductor or semiconductor material and a liquid crystalline organic compound together and aligning molecules of the carbon nanotube favorably and densely by utilizing favorable orientation of the liquid crystalline organic compound of the composite-type material, as well as a thin film transistor employing such a conductive thin film.
  • FIG. 1 is a sectional view schematically illustrating a part of a process for forming a conductive thin film according to embodiment 1 of the present invention.
  • the conductive thin film 1 shown in FIG. 1 is formed in the following manner.
  • two electrodes 3 and 4 of such a material as gold are disposed opposite to each other across a spacing of about 5 ⁇ m on a flexible substrate 2 comprising a thin glass sheet, a plastic substrate or the like.
  • a composite-type compound 7 prepared by mixing metallic carbon nanotube 5 to be described later and a liquid crystalline organic compound 6 is coated so as to cover the opposite electrodes 3 and 4 and the substrate 2 or cover at least the aforementioned spacing, with the liquid crystalline organic compound 6 in the composite-type compound 7 kept in an isotropic phase condition.
  • molecules of the metallic carbon nanotube 5 are randomly and sparsely positioned among molecules of the liquid crystalline organic compound 6 in the isotropic phase, as shown in FIG. 1(a) .
  • the metallic carbon nanotube 5 comprises, for example, a carbon nanotube having a high electric conductivity of (1 to 5) ⁇ 10 3 ⁇ -1 cm -1 and a diameter of 1 to 10 nm and a length of 1 to 5 ⁇ m.
  • the carbon nanotube to be used is not limited to carbon nanotube having the above-noted electrical characteristic and shape but may have a shape and an electrical characteristic whether within or out of the aforementioned ranges.
  • the liquid crystalline organic compound 6 used is 8-PNP-O 4 , which is a molecular compound of a 2-phenylnaphthalene derivative and which has a structure shown in FIG. 6 .
  • the molecular compound 8-PNP-O 4 is used in a smectic phase, either SmA phase or SmE phase, among liquid crystalline phases thereof. Note that the compound 8-PNP-O 4 exhibits an isotropic phase at a temperature not lower than 129°C, SmA phase at a temperature between 125°C and 129°C, and SmE phase at a temperature between 55°C and 125°C.
  • the coat of the composite-type compound 7 with the liquid crystalline organic compound 6 kept in the isotropic phase is gradually cooled to hold the liquid crystalline organic compound 6 in SmA or SmE phase.
  • the SmA phase and the SmE phase each have such a high degree of molecular orientational order as can be regarded as a flexible crystal.
  • 8-PNP-O 4 molecules of the liquid crystalline organic compound 6 in SmA or SmE phase as a smectic phase having a high degree of molecular orientational order are favorably and homogeneously oriented.
  • the metallic carbon nanotube 5 mixed therewith becomes oriented favorably in the composite-type compound 7.
  • the conductive thin film 1 is formed by such a simple and convenient method as to align and orient carbon nanotubes 5 densely in the degree of molecular orientational order improved by utilizing the liquid crystallinity of the liquid crystalline organic compound 6.
  • the density of electronic contacts between adjacent molecules of the carbon nanotube 5 can be increased.
  • the conductive thin film 1 which was formed by the above-described method to comprise the composite-type compound 7 prepared by mixing the metallic carbon nanotube 5 and the liquid crystalline organic compound 6 and have an improved degree of molecular orientational order as compared with the prior art, had a very high electric conductivity as high as about 5 ⁇ 10 2 ⁇ -1 cm -1 .
  • a conductive thin film having a lower degree of orientation of carbon nanotube which was formed by the prior art to comprise a similar composite-type compound prepared by using similar carbon nanotube, had a low electric conductivity as low as about 10 ⁇ -1 cm -1 .
  • the conductive thin film according to the present invention can have an improved fill density of carbon nanotube by orienting molecules of the liquid crystalline organic compound of the composite-type compound in a predetermined direction to causes carbon nanotube molecules mixed in the composite-type compound to be aligned favorably and densely. For this reason, the density of electronic contacts between adjacent carbon nanotube molecules can be increased, which makes it possible to improve the electric conductivity of the conductive thin film by leaps and bounds.
  • the use of a conductive thin film of such a structure makes it possible to provide an organic-type conductive thin film which is excellent in characteristics and adaptable to a low-temperature process for realizing components for use in microcircuit devices, high-performance electronic devices and the like or wiring materials.
  • the present embodiment described above utilizes a smectic phase, either SmA phase or SmE phase, of the 2-phenylnaphthalene derivative used as the liquid crystalline organic compound
  • the present invention can be practiced by using such a liquid crystalline phase as SmB phase without limitation to this embodiment.
  • 8-PNP-O 4 which is a 2-phenylnaphthalene derivative, as the liquid crystalline organic compound
  • a smectic phase either SmA phase or SmB phase
  • 8-PNP-O 12 or a nematic phase of 5-PNP-O 1 without limitation to this embodiment.
  • any liquid crystalline organic compound may be used without limitation to this embodiment as long as the liquid crystalline organic compound has a nematic or smectic phase having a high degree of molecular orientational order.
  • FIG. 2 is a sectional view schematically illustrating a part of a process for forming a composite-type semiconductor layer in which a conductive thin film according to embodiment 2 of the present invention is used as a semiconductor layer.
  • the composite-type semiconductor layer 15 as the semiconductor layer 10 in FIG. 2 is formed in the following manner.
  • An orientation film (not shown), such as a polyimide film or a monomolecular film, is formed over a surface of a region in which at least a channel (not shown) is to be formed so as to cover at least a part of each of source and drain electrodes 11 and 12 disposed opposite to each other on a substrate 2 and an upper surface of the substrate 2 lying in the space intervening between these electrodes.
  • the orientation film is then oriented in a predetermined direction by such orientation means as rubbing.
  • a composite-type compound 14 prepared by mixing semiconductive carbon nanotube 13 and a liquid crystalline organic semiconductor compound 16 is coated to the substrate 2.
  • the composite-type compound 14 is injected into a region defined between the substrate 2 including the source and drain electrodes 11 and 12 and the gate insulator 9 extending above the liquid crystalline organic semiconductor compound 16.
  • the semiconductive carbon nanotube 13 comprises, for example, a carbon nanotube having a carrier mobility of about 1000 cm 2 /Vs, a diameter of 1 to 5 nm and a length of about 1 ⁇ m.
  • Such semiconductive carbon nanotubes 13 are selected from mixed-type carbon nanotube comprising metallic carbon nanotubes and semiconductive carbon nanotubes.
  • the liquid crystalline organic compound 16 used is 8-PNP-O 4 , which is a 2-phenylnaphthalene derivative shown in FIG. 6 .
  • the compound 16 is used in a smectic phase, either SmA phase or SmE phase, among liquid crystalline phases thereof.
  • the temperature of the composite-type compound 7 is lowered to hold the liquid crystalline organic semiconductor compound 16 in SmA or SmE phase.
  • the orientation film (not shown) formed on at least the substrate 2 is oriented in the predetermined direction by such orientation means as rubbing, molecules of 8-PNP-O 4 as the liquid crystalline organic semiconductor compound 16 held in SmA or SmE phase as a smectic phase having an excellent degree of molecular orientational order are oriented favorably.
  • Such favorable orientation of 8-PNP-O 4 molecules causes semiconductive carbon nanotubes 13 to be aligned so densely as to improve the degree of molecular orientational order thereof.
  • the composite-type semiconductor layer 15 is advantageously formed as the semiconductor layer 10.
  • the liquid crystalline organic semiconductor compound 16 comprises a compound having a charge transport function.
  • the liquid crystalline organic semiconductor compound 16 comprising 8-PNP-O 4 in SmE phase shown in FIG. 6 has, per se, a carrier mobility of 10 -2 cm 2 /Vs with respect to electron and hole both. This value of carrier mobility is comparable to that of a-Si:H with respect to hole and is close to the maximum carrier mobility value of organic compounds except molecular crystals with respect to electron.
  • the liquid crystalline organic semiconductor compound 16 is favorably oriented while at the same time carbon nanotubes 13 aligned so favorably and densely as to improve the fill density thereof in the mixture. Accordingly, the density of electronic contacts between adjacent carbon nanotube molecules can be increased.
  • the composite-type semiconductor layer 15 as the semiconductor layer 10 which was formed by the above-described method using the composite-type compound 14 prepared by mixing the metallic carbon nanotube 13 and the liquid crystalline organic compound 16 and which had an improved degree of molecular orientational order as compared with the prior art by a simple and convenient method, had a high carrier mobility as high as about 350 cm 2 /Vs.
  • a composite-type semiconductor layer having a lower degree of molecular orientational order which was formed by the prior art using a conventional composite-type semiconductor material prepared by using semiconductive carbon nanotube having similar characteristics to the carbon nanotube 13, had a low carrier mobility as low as about 0.6 cm 2 /Vs.
  • FIG. 3 is a sectional view schematically showing the construction of a thin film transistor according to embodiment 3 of the present invention.
  • the thin film transistor 18a has source and drain electrodes 11 and 12 formed on a substrate 2 by patterning such an electrode material as gold.
  • the thin film transistor 18a also has a composite-type semiconductor layer 15 formed as semiconductor layer 10 by a method to be described later, the composite-type semiconductor layer 15 being interposed between the source and drain electrodes 11 and 12 and a gate insulator 9 to be described later.
  • the gate insulator 9 comprising silicon oxide, a polyvinylidene fluoride organic compound or the like.
  • the thin film transistor 18a further has a gate electrode 17 formed of such an electrode material as gold on the upper side of the gate insulator 9.
  • the source and drain electrodes 11 and 12, gate insulator 9 and gate electrode 17 are sequentially patterned by utilizing a thin film deposition technique, photolithography, lift-off technique and the like.
  • the thin film transistor 18a of the top-gated type having the gate electrode 17 disposed on top is constructed as shown in FIG. 3 .
  • such components as a cap layer and a sealing film for sealing the semiconductor layer 10 are not illustrated in FIG. 3 .
  • the composite-type semiconductor layer 15 as the semiconductor layer 10 in FIG. 3 is formed in the following manner.
  • An orientation film (not shown), such as a polyimide film or a monomolecular film, is formed over a surface of a region in which at least a channel (not shown) is to be formed so as to cover at least a part of each of source and drain electrodes 11 and 12 disposed opposite to each other on the substrate 2 and an upper surface of the substrate 2 lying in the space intervening between these electrodes.
  • the orientation film is then oriented in a predetermined direction by such orientation means as rubbing.
  • a composite-type compound 14 prepared by mixing semiconductive carbon nanotube 13 and a liquid crystalline organic semiconductor compound 16 is coated over the source and drain electrodes 11 and 12 and the substrate 2. With the channel (not shown) of the thin film transistor 18a centered between the source and drain electrodes 11 and 12, the gate insulator 9 is formed over the semiconductor layer 10.
  • the composite-type compound 14 may be injected between the substrate 2 and the gate insulator 9.
  • the semiconductive carbon nanotube 13 comprised, for example, semiconductive carbon nanotube having a carrier mobility of about 1000 cm 2 /Vs, a diameter of 1 to 5 nm and a length of about 1 ⁇ m which was selected from mixed carbon nanotube comprising metallic carbon nanotubes and semiconductive carbon nanotubes.
  • the liquid crystalline organic semiconductor compound 16 used in this embodiment is 8-PNP-O 4 , which is a molecular compound of a 2-phenylnaphthalene derivative having the structure shown in FIG. 6 .
  • the compound 16 is used in a smectic phase, either SmA phase or SmE phase, among liquid crystalline phases thereof.
  • the compound 8-PNP-O 4 exhibits an isotropic phase at a temperature not lower than 129°C, SmA phase at a temperature between 125°C and 129°C, and SmE phase at a temperature between 55°C and 125°C.
  • the composite-type compound 14 is prepared by mixing the liquid crystalline organic semiconductor compound 16 in an isotropic phase and semiconductive carbon nanotube 13 together and coated to the substrate 2. By lowering the temperature of the composite-type compound 14 thus coated, the liquid crystalline organic compound 16 is held in SmA or SmE phase.
  • SmA phase or SmE phase has such a high degree of molecular orientational order as can be regarded as a flexible crystal.
  • the orientation film (not shown) formed on at least the substrate 2 is oriented in the predetermined direction by such orientation means as rubbing, molecules of 8-PNP-O 4 used as the liquid crystalline organic semiconductor compound 16 in SmA or SmE phase as a smectic phase having an excellent degree of molecular orientational order are oriented favorably.
  • Such favorable orientation of 8-PNP-O 4 molecules causes semiconductive carbon nanotubes 13 mixed with 8-PNP-O 4 to be aligned so densely and favorably as to improve the degree of molecular orientational order thereof.
  • the liquid crystalline organic semiconductor compound 16 having the charge transport function is favorably oriented while at the same time semiconductive carbon nanotubes 13 aligned so favorably and densely as to improve the fill density thereof in the mixture. Accordingly, the density of electronic contacts between adjacent carbon nanotube molecules can be increased, whereby the composite-type semiconductor layer 15 can be used as favorable semiconductor layer 10. That is, the composite-type semiconductor layer 15 is advantageously formed as the semiconductor layer 10.
  • the composite-type semiconductor layer 15 as the semiconductor layer 10 which comprised the composite-type compound 14 prepared by mixing the carbon nanotube 13 and the liquid crystalline organic semiconductor compound 16 together and had a degree of molecular orientational order that was improved as compared with the prior art by a simple and convenient method, had a high carrier mobility as high as about 350 cm 2 /Vs.
  • a thin film transistor having a composite-type semiconductor layer having a lower degree of molecular orientational order which was formed by the prior art to comprise a conventional composite-type semiconductor material prepared by using semiconductive carbon nanotube having similar characteristics to the carbon nanotube 13, had a low carrier mobility at channel as low as about 0.6 cm 2 /Vs.
  • the composite-type semiconductor layer 15 comprises the composite-type compound 14, it is possible to orient molecules of the liquid crystalline organic semiconductor compound 16 as well as to align semiconductive carbon nanotubes 13 mixed therewith favorably and densely in accordance with the orientation of the liquid crystalline organic semiconductor compound 16 in the composite-type semiconductor layer 15.
  • the conventional orientation means can be employed as means for orienting the liquid crystalline organic semiconductor compound 16
  • the carbon nanotube 13 can be oriented by a simple and convenient method.
  • Such a simple and convenient method makes it possible to improve the fill density of carbon nanotube 13 and increase the density of electronic contacts between adjacent carbon nanotube molecules. For this reason, it becomes possible to provide the thin film transistor 18a having the semiconductor layer 10 which is improved in carrier mobility at a low price.
  • the semiconductor layer 10 can be improved in carrier mobility, the thin film transistor 18a can be used in microcircuit devices, high-performance electronic devices and the like.
  • the carrier mobility at channel of the thin film transistor 18a can be further enhanced than in cases where a semiconductor layer comprises a mixture of a liquid crystalline organic compound and carbon nanotube.
  • a semiconductor layer comprises a mixture of a liquid crystalline organic compound and carbon nanotube.
  • current in the composite-type semiconductor layer 15 passes through the liquid crystalline organic semiconductor compound 16 and the semiconductive carbon nanotube 13.
  • the use of the liquid crystalline organic semiconductor compound 16 makes it possible to provide the thin film transistor 18a which is more excellent in carrier mobility and on characteristic than the use of a liquid crystalline organic compound.
  • the thin film transistor according to the present embodiment of the invention may be either a top-gated thin film transistor having gate electrode 17 disposed on top of the gate insulator 9 on the opposite side away from the substrate 2 as shown in FIG. 3 or a bottom-gated thin film transistor having gate electrode 17 disposed on the substrate 2 or on the bottom as shown in FIG. 4 showing a different structure from that shown in FIG. 3 .
  • FIG. 4 is a sectional view schematically showing the construction of a bottom-gated thin film transistor having a gate electrode disposed on a substrate or on the bottom according to the present embodiment.
  • the bottom-gated thin film transistor 18b has the gate electrode 17 disposed on the upper side of the substrate 2 unlike the top-gated thin film transistor 18a shown in FIG. 3 .
  • the gate insulator 9 extends to cover the gate electrode 17 and the exposed portion of the substrate 2.
  • Semiconductor layer 10 and source and drain electrodes 11 and 12 are disposed on the upper side of the gate insulator 9.
  • the gate electrode 17 is formed on the upper side of the substrate and then the gate insulator 9 formed to extend to cover the gate electrode 17 and the exposed portion of the substrate 2.
  • the source and drain electrodes 11 and 12 are disposed opposite to each other on the upper side of the gate insulator 9.
  • the composite-type compound 14 comprising a mixture of the semiconductive carbon nanotube 13 and the liquid crystalline organic semiconductor compound 16 is coated to at least the upper side of the gate insulator so as to extend over the pair of opposite source and drain electrodes 11 and 12 or cover the space between the source and drain electrodes 11 and 12.
  • the layer of the composite-type compound 14 is applied with a shear stress in a substantially fixed direction by means of a roll coater (not shown) or the like.
  • a roll coater not shown
  • the composite-type semiconductor layer 15 thus treated, it becomes possible that molecules of the liquid crystalline organic semiconductor compound 16 are favorably oriented while at the same time semiconductive carbon nanotubes 13 aligned so favorably and densely as to improve the fill density thereof in the mixture. Accordingly, the density of electronic contacts between adjacent carbon nanotube molecules can be increased.
  • the material usable for the gate electrode 17 and the source and drain electrodes 11 and 12 may be any material which has electric conductivity and is unreactive to each of the substrate 2 and the semiconductor layer 10.
  • examples of such usable materials include doped silicon, precious metals such as gold, silver, platinum and palladium, alkali metals or alkali earth metals such as lithium, cesium, calcium and magnesium, and metals such as copper, nickel, aluminum, titanium and molybdenum, or alloys thereof.
  • Other usable materials include conductive organic compounds such as polypyrrole, polythiophene, polyaniline and polyphenylenevinylene.
  • the gate electrode 17 since the thin film transistor 18a or 18b is operable if the gate electrode 17 has a higher electric resistance than other electrodes (source and drain electrodes 11 and 12), the gate electrode 17 in particular may comprise a material different from that of the source and drain electrodes 11 and 12 for easy fabrication.
  • a room-temperature process which achieves deposition and formation at room temperature or at a temperature close to room temperature, can be applied to but not necessarily required for these electrode materials.
  • the material usable for the aforementioned gate insulator 9 may be any material which has an electric insulating property and is unreactive to each of the substrate 2, electrodes and the semiconductor layer 10.
  • the substrate 2 and the gate insulator 9 may be in a form wherein a typical silicon oxide film is formed on silicon so as to be used as the gate insulator, or in a form wherein a thin layer of resin or the like is formed after the formation of an oxide film so as to function as the gate insulator.
  • the gate insulator 9 may be formed by deposition of a compound consisting of elements different from those forming the substrate 2 and the electrodes by means of CVD, vapor deposition, sputtering or the like, or by coating, spraying, electrodeposition or the like of a solution of such a compound. Since it is known that a material having a high dielectric constant is used as the material of gate insulator 9 in order to lower the gate voltage of the thin film transistor 18a or 18b, the gate electrode 9 may be formed using a compound having a high dielectric constant other than ferroelectric compounds and ferroelectrics. Besides inorganic materials, it is possible to use organic materials having high dielectric constants such as polyvinylidene fluoride compounds, polyvinylidene cyanide compounds and the like.
  • embodiments 2 and 3 of the present invention each utilize a smectic phase, either SmA phase or SmE phase, of the 2-phenylnaphthalene derivative compound used as the liquid crystalline organic semiconductor compound 16, the present invention may be practiced by utilizing such a liquid crystalline phase as SmB phase. Also, though these embodiments each use 8-PNP-O 4 , which is a 2-phenylnaphthalene derivative, as the liquid crystalline organic semiconductor compound 16, it is possible to utilize a smectic phase of 8-PNP-O 12 .
  • Examples of such 6 ⁇ -electron aromatic rings include benzene ring, pyridine ring, pyrimidine ring, pyridazine ring, pyrazine ring, and tropolone ring.
  • Examples of such 10 ⁇ -electron aromatic rings include naphthalene ring, azulene ring, benzofuran ring, indole ring, indazole ring, benzothiazole ring, benzoxazole ring, benzimidazole ring, quinoline ring, isoquinoline ring, quinazoline ring, and quinoxaline ring.
  • Examples of such 14n-electron aromatic rings include phenanthrene ring, and anthracene ring.
  • liquid crystalline organic semiconductor compound having at least one of 2-phenylnaphthalene ring, biphenyl ring, benzothiazole ring and t-thiophene ring in the core thereof and a rod-like molecular structure.
  • a more preferable liquid crystalline organic semiconductor compound has 2-phenylnaphthalene ring in the core thereof and benzene ring and naphthalene ring each having an alkyl, alkoxy or a like group as a side chain and a rod-like molecular structure.
  • the liquid crystalline organic compound or liquid crystalline organic semiconductor compound to be used in practicing the present invention may be any liquid crystalline organic compound or liquid crystalline organic semiconductor compound which has a nematic phase having a higher degree of molecular orientational order or the aforementioned other smectic phase.
  • the liquid crystalline organic compound or liquid crystalline organic semiconductor compound and the nanotube material are mixed together at an adjusted mixture ratio.
  • the mixture ratio of carbon nanotube to the whole mixture is preferably 30 to 90% by volume, desirably 50 to 70% by volume.
  • the mixture prepared at that mixture ratio is easy to handle. The optimum mixture ratio may be appropriately adjusted to the materials used, process conditions and desired characteristics even if the adjusted ratio is out of the aforementioned range.
  • a conductive thin film or semiconductor layer having further improved carrier mobility or electric conductivity is formed from a composite-type compound prepared by mixing the liquid crystalline organic compound or liquid crystalline organic semiconductor compound with carbon nanotube, which is an inorganic material.
  • a composite-type compound prepared by mixing the liquid crystalline organic compound or liquid crystalline organic semiconductor compound with carbon nanotube, which is an inorganic material.
  • a resin film substrate having suppleness such as a thin polyimide film may be used as the aforementioned substrate 2.
  • a resin film substrate having suppleness such as a thin polyimide film
  • Such a film can provide for a flexible paper display, sheet display or the like having a substrate comprising a plastic sheet or a resin film.
  • the thin film transistors 18a and 18b according to the present invention each have the semiconductor layer 10 comprising the composite-type semiconductor layer 15 composed of at least the liquid crystalline organic semiconductor compound 16 and the carbon nanotube 13 and having an improved degree of orientation.
  • Each of the on-state characteristic value and off-state characteristic value of such a thin film transistor is higher than an intermediate characteristic value between the on- or off-state characteristic value of a conventional thin film transistor having a semiconductor layer comprising only the liquid crystalline organic semiconductor compound 16 and the on- or off-state characteristic value of a conventional thin film transistor having a semiconductor layer comprising only the carbon nanotube 13. For this reason, if one of the on-state characteristic and the off-state characteristic is insufficient, improvement can be made by the present invention.
  • a thin film transistor having a semiconductor layer comprising only the liquid crystalline organic semiconductor compound having a low carrier mobility needs to have a gate width of about several hundred ⁇ m, while a thin film transistor having a semiconductor layer comprising only the semiconductive carbon nanotube having a very high carrier mobility needs to have a very small gate width of about 0.1 ⁇ m. Either case is not practical.
  • the carrier mobility of the composite-type semiconductor layer composed of the liquid crystalline organic semiconductor compound and the carbon nanotube and imparted with a favorable orientation assumes a higher value than the intermediate value between the values of carrier mobility of the two conventional transistors. Therefore, it is possible to make designing and fabrication based on a practical gate width of about several ⁇ m and use a long and wide channel region.
  • the channel dimensions can be designed to meet the electric conductivities in the on-state and the off-state. That is, the composite-type semiconductor layer of the thin film transistor according to the present invention can be regarded as a composite-type semiconductor layer wherein the advantages of respective of the liquid crystalline organic semiconductor compound and the carbon nanotube are reinforced such that the advantage of the carbon nanotube compensates for the disadvantage of the liquid crystalline organic semiconductor compound while the advantage of the liquid crystalline organic semiconductor compound compensates for the disadvantage of the carbon nanotube.
  • FIG. 5 is a diagram schematically illustrating the configuration of one exemplary image display device using a semiconductor circuit device comprising a thin film transistor according to the present invention.
  • an active-matrix image display device 19 (display) is constructed using plural thin film transistors (not shown) each having a composite-type semiconductor layer as a semiconductor layer according to embodiment 3 at least as switching devices associated with pixels.
  • the image display device 19 thus constructed is capable of turning ON/OFF an information signal by means of the switching devices (not shown) each located adjacent an associated one of intersections 23 of plural electrodes 21 and plural electrodes 22 arranged in a matrix pattern on a plastic substrate 20 or the like, the switching devices each comprising a very small thin film transistor (not shown).
  • the switching devices each located adjacent an associated one of intersections 23 of plural electrodes 21 and plural electrodes 22 arranged in a matrix pattern on a plastic substrate 20 or the like, the switching devices each comprising a very small thin film transistor (not shown).
  • driver circuits 24a and 24b and control circuit 25 which are located in the periphery of the display, are formed using the aforementioned conductive thin film or thin film transistor (not shown), the display panel 26 and the aforementioned circuits can be formed integrally. For this reason, it is possible to construct a flexible image display device, such as a rewritable paper-like electronic display or a sheet display, which has a more improved mechanical reliability than an image display device using a conductive thin film or thin film transistor comprising only nanotube.
  • a paper-like or sheet-shaped display panel as the active-matrix display panel can employ display panel types including the liquid crystal display type, organic EL type, electrochromic display type (ECD), electrolytic deposition type, electronic particulate material type, and coherent modulation type (MEMS), and the like.
  • display panel types including the liquid crystal display type, organic EL type, electrochromic display type (ECD), electrolytic deposition type, electronic particulate material type, and coherent modulation type (MEMS), and the like.
  • a radio-frequency IC tag which, as a whole, is more flexible and harder to break than a conventional radio-frequency IC tag comprising a silicon chip. It is also possible to use a semiconductor circuit device incorporating the aforementioned conductive thin film or thin film transistor in a mobile device, disposable device, other electronic device or the like.
  • Embodiments 4 and 5 of the present invention to be described below are embodiments realizing a conductive thin film which is further improved in electric conductivity and carrier mobility and which is formed so as to orient molecules of an organic semiconductor compound in a predetermined direction by such simple, convenient and less costly means as to prepare a liquid crystalline organic semiconductor mixture exhibiting liquid crystallinity by hydrogen-bonding a non-liquid-crystalline organic semiconductor compound and a non-liquid-crystalline organic compound together and orient the liquid crystalline organic semiconductor mixture in a predetermined direction, as well as a thin film transistor using such a conductive thin film.
  • FIG. 7 is a sectional view schematically illustrating a process for forming a conductive thin film according to embodiment 4 of the present invention. For the purpose of avoiding complicated description, the illustration of the process is partially omitted in FIG. 7 .
  • a method of forming a conductive thin film will be described with reference to FIG. 7 .
  • an organic semiconductor compound material comprising a non-liquid-crystalline pentacene derivative shown in FIG. 11(a) and a non-liquid-crystalline organic compound shown in FIG. 11(b) are mixed together at a molar ratio of about 1:1.
  • the pentacene derivative compound shown in FIG. 11(a) is a compound wherein at least one carbon atom of a benzene ring located at at least a terminal of pentacene as an organic semiconductor compound material is substituted with nitrogen (N) atom, which is electrically more negative than hydrogen atom.
  • the non-liquid-crystalline organic compound shown in FIG. 11(b) is a benzoic acid derivative having a carboxy group.
  • the benzoic acid derivative shown in FIG. 11(b) desirably has an alkoxy group having at least about three to eight carbon atoms, but is not limited thereto.
  • the benzoic acid derivative is used as the non-liquid-crystalline organic compound in the above description, it is possible to use a biphenylcarboxylic acid derivative.
  • the "supermolecular”, as used herein, is meant to represent such a structure of the liquid crystalline organic semiconductor mixture prepared by mixing the pentacene derivative and the benzoic acid derivative together as to exhibit liquid crystallinity, which is a new property, despite the fact that the pentacene derivative and the benzoic acid derivative, singly, exhibit neither molecular orientation nor liquid crystallinity.
  • the aforementioned liquid crystalline organic semiconductor mixture is a mixture produced based on hydrogen bond having a lower bonding power than covalent bond, the liquid crystalline organic semiconductor mixture is a stable material which can be handled in a process at a temperature close to room temperature.
  • At least two electrodes 3 and 4 are disposed opposite to each other on a substrate 2 comprising a glass or plastic substrate or a like substrate, as shown in FIG. 7(a) .
  • a polyimide film having a thickness of 100 nm is formed by spin coating and then baked to form an orientation film (not shown) on the substrate 2. Then, at least a portion of the orientation film extending between the electrodes 3 and 4 is subjected to an orientation treatment.
  • the orientation treatment is rubbing of the orientation film surface with dust-free cloth in a predetermined direction, for example, in the direction from the electrode 3 toward the electrode 4 (indicated by arrow).
  • the non-liquid-crystalline pentacene derivative (see FIG. 11(a) ) and the non-liquid-crystalline benzoic acid derivative (see FIG. 11(b) ) are mixed together to prepare a liquid crystalline organic semiconductor mixture 27 given a supermolecular structure based on hydrogen bond.
  • the liquid crystalline organic semiconductor mixture 27 thus prepared is applied to a thickness of about 1 ⁇ m over the orientation film, which has undergone the orientation treatment in the step of FIG. 7(a) , on the substrate 2 by casting.
  • the longitudinal axes of supermolecules in the supermolecular structure of the liquid crystalline organic semiconductor mixture 27 exhibiting a smectic phase are oriented in the predetermined direction indicated by arrow, which causes the longitudinal axes of molecules of the pentacene derivative to be oriented in a desired direction, molecules of the pentacene derivative being constituent molecules of the supermolecules.
  • the longitudinal axes of pentacene derivative molecules, which are internal constituent molecules present in the liquid crystalline organic semiconductor mixture 28, are aligned in a desired fixed direction, for example, in the direction from the electrode 3 toward the electrode 4, relative to the molecules of the liquid crystalline organic semiconductor mixture 28 oriented in the fixed predetermined direction by the orientation treatment. Accordingly, by adjusting the alignment direction of the liquid crystalline organic semiconductor mixture 27 to a predetermined direction by means of the aforementioned orientation treatment, it is possible to adjust alignment of the longitudinal axes of the organic semiconductor compound to a desired direction.
  • a desired fixed direction for example, in the direction from the electrode 3 toward the electrode 4
  • the aforementioned predetermined direction and the aforementioned desired direction are substantially the same as the direction across the electrodes (indicated by arrow). Note that some combinations of compounds to be used may cause the desired direction to differ from the predetermined direction, which is the orientation treatment direction and, therefore, the predetermined direction need be selected so that the desired direction is obtained as intended.
  • the conductive thin film 28 according to the present embodiment, wherein the longitudinal axes of pentacene derivative molecules in the liquid crystalline organic semiconductor mixture 27 are oriented in the desired direction, allows charge transfer in the direction across the electrodes to be made smoothly and is improved in electric conductivity and carrier mobility.
  • FIG. 8 is a sectional view schematically showing the structure of another conductive thin film according to embodiment 4 of the present invention.
  • a conductive thin film 29 shown in FIG. 8 is different from the conductive thin film 28 shown in FIG. 7 in that an organic compound component as constituent molecules that are unnecessary from at least the viewpoint of charge transfer is removed from the liquid crystalline organic semiconductor mixture 27 forming the conductive thin film 28 shown in FIG. 7(c) .
  • the benzoic acid derivative component which is an organic compound acting to impede charge transfer is removed from the liquid crystalline organic semiconductor mixture 27 having a supermolecular structure based on hydrogen bond between the non-liquid-crystalline pentacene derivative shown in FIG. 11(a) and the non-liquid-crystalline benzoic acid derivative shown in FIG. 11(b) , which are mixed together to form the liquid crystalline organic semiconductor mixture 27.
  • the liquid crystalline organic semiconductor mixture 27 is heated to break the hydrogen bond thereby causing the benzoic acid derivative component to dissipate.
  • the benzoic acid derivative shown in FIG. 11(b) as constituent molecules - that were unnecessary from the viewpoint of charge transfer was caused to sublimate and dissipate.
  • the conductive thin film 29 having favorable characteristics could be formed in which only the pentacene derivative shown in FIG. 11(a) remained as the organic semiconductor compound oriented in the predetermined direction.
  • the structure of the other conductive thin film 29 formed using the pentacene derivative organic semiconductor according to the present embodiment exhibited a further improved carrier mobility as high as about 1.0 cm 2 /Vs, which confirmed that it was possible to form a conductive thin film having a carrier mobility that was more improved than the high carrier mobility of the pentacene organic semiconductor compound.
  • the value of carrier mobility exhibited is higher than the carrier mobility (about 0.6 cm 2 /Vs) of the crystal phase of a pentacene organic semiconductor formed by the conventional vapor deposition. It was also confirmed that the conductive thin film 29 could be stably formed over a large area of 100 ⁇ 100 mm on a supple substrate substantially uniformly and any defect did not occur even when the plastic substrate was subjected to certain flexing.
  • the method of removing the organic compound impeding charge transfer from the liquid crystalline organic semiconductor mixture 27 includes heating the liquid crystalline organic semiconductor mixture 27 to remove the unnecessary organic compound; however, there is no limitation to this method.
  • the conductive thin film according to the present invention can be stably formed to have a carrier mobility that is more improved than the high carrier mobility of the organic semiconductor compound by a simple and convenient method which includes: preparing the liquid crystalline organic semiconductor mixture by mixing the non-liquid-crystalline organic semiconductor compound and the non-liquid-crystalline organic compound together to allow these compounds to be hydrogen-bonded; coating the mixture to a predetermined region; and orienting the mixture in the predetermined direction thereby causing at least the organic semiconductor compound to be oriented in the predetermined direction.
  • the structure of the other conductive thin film according to the present invention it is possible to further improve the carrier mobility of the conductive thin film than the high carrier mobility of the organic semiconductor compound and form the conductive thin film stably by removing at least the organic compound component acting to impede charge transfer from the liquid crystalline organic semiconductor mixture.
  • While the present embodiment uses the pentacene derivative shown in FIG. 11(a) which is substituted with one nitrogen atom, it is possible to use a pentacene derivative in which plural carbon atoms are substituted with nitrogen atoms without limitation on the above-noted mixture ratio thereof.
  • a pentacene derivative molecule substituted with two nitrogen atoms can form a double hydrogen bond to two molecules of the benzoic acid derivative shown in FIG. 11(b) , to give a liquid crystalline organic semiconductor mixture having a supermolecular structure as shown in FIG. 11(d) .
  • Methods of coating of the liquid crystalline organic semiconductor mixture 27 which can be employed in the above-described embodiment include dropping, spinner coating, dip coating, such printing as screen printing, roll coating, ink-jet coating, spray coating, and other coating methods, in addition to the aforementioned casting.
  • Methods of orienting the conductive thin film 28,29 or organic semiconductor thin film comprising the liquid crystalline organic semiconductor mixture 27 in the predetermined direction include: a method including forming the conductive thin film or organic semiconductor film over an orientation film having subjected to the orientation treatment; a method including applying the conductive thin film or organic semiconductor film with an electric field; and a method including applying the conductive thin film or organic semiconductor film with a magnetic field. These orientation treatment methods are applicable to all the embodiments of the present invention.
  • inorganic-type orientation films such as a silicon oxide film or the like
  • organic-type orientation films such as a nylon film, polyvinyl alcohol film, polyimide film, and monomolecular film.
  • These orientation films are formed by oblique vapor deposition or rotary vapor deposition and
  • FIG. 9 is a sectional view schematically showing the construction of a thin film transistor according to embodiment 5 of the present invention.
  • the thin film transistor 30 shown in FIG. 9 includes a gate electrode 17 of a desired shape formed on an insulating substrate 2, and a semiconductor layer 31 forming a channel layer and formed above the gate electrode 17 with an intervening gate insulator 9 therebetween. Also, source electrode 11 and drain electrode 12 are formed between the insulating substrate 2 and the semiconductor layer 31 so as to connect directly to the semiconductor layer 31. Usually, a cap layer is stacked over the gate electrode 17, source and drain electrodes 11 and 12 and semiconductor layer 31. Further, lead electrodes, which are not shown for avoiding complicated illustration, are connected to respective of the source and drain electrodes 11 and 12.
  • FIG. 10 is a sectional view schematically illustrating a process for fabricating the thin film transistor according to the present embodiment.
  • some conventional parts or components required in fabricating the thin film transistor are omitted for avoiding complicated illustration.
  • an aluminum film is formed to a thickness of 300 nm on a surface of the insulating substrate 2 comprising a plastic substrate or a glass substrate.
  • the aluminum film thus formed is patterned by photolithography and etching to form the gate electrode 17.
  • a polyimide film having a thickness of 100 nm is formed to cover the gate electrode 17 and the exposed portion of the substrate 2 by spin coating, thus forming the gate insulator 9.
  • an indium tin oxide film (ITO) as a conductive thin film is formed to a thickness of 300 nm on the gate insulator 9 by EB evaporation at a substrate temperature of 100°C and then subjected to photolithography and etching to form the source and drain electrodes 11 and 12.
  • ITO indium tin oxide film
  • At least a portion of the gate insulator 9 lying between the source and drain electrodes 11 and 12 is subjected to an orientation treatment.
  • the source and drain electrodes 11 and 12 may be formed on the polyimide gate insulator 9 having subjected to the orientation treatment.
  • the method of orientation treatment employed here includes rubbing the surface of the gate insulator 9 with dust-free cloth in a predetermined direction, for example, in one direction across the source and drain electrodes 11 and 12 (indicated by arrow), like the method employed in embodiment 4.
  • Such an orientation treatment allows the longitudinal axes of supermolecules of liquid crystalline organic semiconductor mixture 27 (to be described later) to be oriented and aligned in a direction parallel with the rubbing direction.
  • the semiconductor layer 31 comprising an organic semiconductor film is formed on the gate insulator 9 to serve as a channel layer, as shown in FIG. 9 .
  • the semiconductor layer 31 comprising the organic semiconductor film is formed in the following manner as in the formation of the conductive thin film of embodiment 4.
  • the non-liquid-crystalline pentacene derivative shown in FIG. 11(a) and the non-liquid-crystalline benzoic acid derivative shown in FIG. 11(b) are mixed together to prepare the liquid crystalline organic semiconductor mixture 27 given a supermolecular structure based on hydrogen bond as shown in FIG. 11(c) .
  • the liquid crystalline organic semiconductor mixture 27 thus prepared is coated to the substrate 2, which has undergone the orientation treatment in the step shown in FIG. 10(a) , to a thickness of about 1 ⁇ m so as to cover at least the source and drain electrodes 11 and 12 on the substrate 2 by casting.
  • liquid crystalline organic semiconductor mixture 27 exhibiting a smectic phase
  • the longitudinal axes of molecules of the supermolecular structure thus formed in the predetermined direction indicated by arrow
  • the longitudinal axes of pentacene derivative molecules, which are internal constituent molecules present in the liquid crystalline organic semiconductor mixture 27, are aligned in a desired direction that is substantially fixed, for example, in the direction from the source electrode 11 to the drain electrode 12 (indicated by arrow), relative to the molecules of the liquid crystalline organic semiconductor mixture 27 oriented in the predetermined fixed direction by the orientation treatment.
  • the aforementioned predetermined direction and the aforementioned desired direction are substantially the same as the direction across the electrodes (indicated by arrow). Note that some combinations of compounds to be used may cause the desired direction to differ from the predetermined direction, which is the orientation treatment direction and, therefore, the predetermined direction need be selected so that the desired direction is obtained as intended.
  • the benzoic acid derivative component which is an organic compound acting to impede charge transfer is removed from the liquid crystalline organic semiconductor mixture 27 in which the non-liquid-crystalline pentacene derivative shown in FIG. 11(a) and the non-liquid-crystalline benzoic acid derivative shown in FIG. 11(b) are mixed together and hydrogen-bonded to each other.
  • the liquid crystalline organic semiconductor mixture 27 is heated to break the hydrogen bond thereby causing the benzoic acid derivative component to dissipate.
  • the thin film transistor 30 was fabricated having the conductive thin film 31 which was oriented in the predetermined direction and in which the pentacene derivative remained as the organic semiconductor compound.
  • the thin film transistor having the semiconductor layer comprising the pentacene derivative organic semiconductor film which was formed by the simple and convenient method according to the present embodiment, exhibited a high carrier mobility at channel as high as about 1.0 cm 2 /Vs. That is, the present embodiment was confirmed to be capable of forming a thin film transistor having a more improved carrier mobility than the high carrier mobility of the pentacene organic semiconductor compound.
  • the value of carrier mobility exhibited is higher than the carrier mobility (about 0.6 cm 2 /Vs) of a thin film transistor having a pentacene organic semiconductor crystal phase formed by the conventional vapor deposition.
  • the present embodiment was also confirmed to be capable of stably forming multiple thin film transistors 30 each having a semiconductor layer comprising conductive thin film 31 from which the benzoic acid derivative component as the organic compound was removed on a flexible substrate having dimensions of 100 ⁇ 100 mm. Further, it was confirmed that any defect was not likely to occur among the multiple thin film transistors even when the plastic substrate was subjected to certain flexing.
  • the present embodiment makes it possible to orient the organic semiconductor compound in the predetermined direction by orienting in the predetermined direction the liquid crystalline organic semiconductor mixture which is prepared by mixing the non-liquid-crystalline organic semiconductor compound and the non-liquid-crystalline organic compound together to allow these compounds to be hydrogen-bonded to each other.
  • the present embodiment which forms the organic semiconductor film by removing the organic compound acting to impede charge transfer by simple and convenient means, makes it possible to provide a thin film transistor having favorable electrical characteristics including a more improved carrier mobility than a high carrier mobility inherent to the organic semiconductor compound.
  • the thin film transistor according to the present embodiment can be provided as a thin film transistor having excellent electrical characteristics and hence are applicable to microcircuit devices, high-performance electronic devices and the like.
  • the above-described thin film transistor according to the present embodiment comprises the gate insulator, the semiconductor layer disposed in contact with the gate insulator, the gate electrode disposed in contact with one side of the gate insulator on the side opposite away from the semiconductor layer, and the source and drain electrodes disposed in contact with at least one side of the semiconductor layer and aligned with the gate electrode so as to be opposed to each other across the gate electrode.
  • the thin film transistor according to the present invention has been described as a bottom-gated thin film transistor having the gate electrode on the substrate, or on the bottom, the thin film transistor of the present invention may be a top gated thin film transistor having the gate electrode on the gate insulator on the side opposite away from the substrate, or on the top.
  • the material usable for the gate electrode 17 and the source and drain electrodes 11 and 12 may be any material which is electrically conductive and unreactive to each of the substrate 2 and the semiconductor layer.
  • examples of such usable materials include doped silicon, precious metals such as gold, silver, platinum and palladium, alkali metals or alkali earth metals such as lithium, cesium, calcium and magnesium, and metals such as copper, nickel, aluminum, titanium and molybdenum, or alloys thereof.
  • Other usable materials include conductive organic materials such as polypyrrole, polythiophene, polyaniline and polyphenylenevinylene. Since the thin film transistor is operable if the gate electrode has a higher electric resistance than other electrodes, the gate electrode in particular may comprise a material different from that of the source and drain electrodes.
  • the material usable for the aforementioned gate insulator 9 may be any material which has an electric insulating property and is unreactive to any one of the substrate 2, electrodes and semiconductor layer.
  • the substrate 2 and the gate insulator 9 may be in a form wherein a typical silicon oxide film is formed on silicon so as to be used as the gate insulator, or in a form wherein a thin layer of resin or the like is formed after the formation of an oxide film so as to function as the gate insulator.
  • the gate insulator 9 may be, formed by deposition of a compound consisting of elements different from those forming the substrate 2 and from those forming the electrodes by means of CVD, vapor deposition, sputtering or the like, or by coating, spraying, electrodeposition or the like of a solution of such a compound. Since it is known that a material having a high dielectric constant is used as the material of gate insulator 9 in order to lower the gate voltage of the thin film transistor 30, the gate insulator 9 may be formed using a compound having a high dielectric constant other than ferroelectric compounds and ferroelectrics. Besides inorganic materials, it is possible to use organic materials having high dielectric constants such as polyvinylidene fluoride compounds, polyvinylidene cyanide compounds and the like.
  • the present embodiment can use the conventional low-temperature thin film formation technology in the formation of a thin film or a semiconductor layer, it is possible to use, besides a flexible plastic sheet that can be bent and a thin glass substrate, a resin film substrate having suppleness such as a thin polyimide film as the aforementioned substrate 2.
  • a resin film substrate having suppleness such as a thin polyimide film as the aforementioned substrate 2.
  • polyethylene film, polystyrene film, polyester film, polycarbonate film, polyimide film and a like film can provide for a flexible paper display, sheet display or the like having a substrate comprising a plastic sheet or a resin film.
  • the thin film transistor fabrication method according to the present invention is capable of forming a conductive thin film oriented in a desired direction simply and conveniently by coating a substrate with the liquid crystalline organic semiconductor mixture prepared by mixing the non-liquid-crystalline organic semiconductor compound and the non-liquid-crystalline organic compound together to allow these compounds to be hydrogen-bonded to each other and orienting the resulting film in a predetermined direction. Also, since it is possible to remove the organic compound impeding at least charge transfer from the liquid crystalline organic semiconductor mixture by a simple and convenient method, a thin film transistor having a semiconductor layer comprising a conductive thin film having a more improved carrier mobility than the high carrier mobility inherent to the organic semiconductor compound can be fabricated inexpensively.
  • the pentacene derivative and the benzoic acid derivative are hydrogen-bonded to each other to give the liquid crystalline organic semiconductor mixture.
  • the liquid crystalline organic semiconductor mixture may comprise any organic semiconductor compound and any organic compound as long as the liquid crystalline organic semiconductor mixture exhibits liquid crystallinity resulting from hydrogen-bonding of the organic semiconductor compound and the organic compound to each other. Therefore, it is required that each of the organic semiconductor compound and the organic compound for use in the present invention have at least one element selected from the group consisting of nitrogen, oxygen, sulfur and halogen atoms which are electrically more negative than hydrogen atom for these compounds to be hydrogen-bonded to each other.
  • the organic semiconductor compound and the organic compound are compounds having respective elements that can be bonded to each other via hydrogen.
  • Each of the organic semiconductor compound and the organic compound for use in the present invention preferably has at least one of an unsaturated bond and a benzene ring which can be bonded to any one selected from the aforementioned group consisting of nitrogen, oxygen, sulfur and halogen atoms.
  • pentacene derivative as the organic semiconductor compound
  • derivatives of acene-type organic semiconductor compounds such as naphthacene and tetracene as well as pentacene
  • derivatives of phthalocyanine-type organic semiconductor compounds such as a copper phthalocyanine derivative
  • derivatives of thiophene-type organic semiconductor compounds such as a copper phthalocyanine derivative
  • the above-described supermolecular structure of the liquid crystalline organic semiconductor mixture exhibiting liquid crystallinity which is prepared by mixing the non-liquid-crystalline organic semiconductor compound and the non-liquid-crystalline organic compound together to allow these compounds to be hydrogen-bonded to each other may be either a substantially rod-like supermolecular structure like a nematic or smectic liquid crystal or a disk-like supermolecular structure such as a discotic liquid crystal.
  • Embodiments 6 and 7 of the present invention to be described below are embodiments realizing a conductive thin film which is further improved in electric conductivity and carrier mobility and which is formed by using a mixed composition layer comprising an organic semiconductor compound having a first liquid crystalline phase of a high order and an organic compound exhibiting a second liquid crystalline phase of a low order and causing the second liquid crystalline phase-of the lower order to be exhibited thereby causing molecules of the organic semiconductor compound to be oriented in a predetermined direction, as well as a thin film transistor employing such a conductive thin film.
  • FIG. 12 is a sectional view schematically illustrating a process for forming a conductive thin film according to embodiment 6 of the present invention. In FIG. 12 , the process is partially omitted for avoiding complicated illustration.
  • the organic semiconductor compound for use in the present embodiment is an organic semiconductor compound having a liquid crystalline phase of a high order at a high temperature (i.e., a liquid crystal phase of low symmetry) or a liquid crystalline phase of a potentially high order.
  • a material comprising at least an organic semiconductor compound having the first liquid crystalline phase of a high order like a smectic liquid crystalline phase at a high temperature is used.
  • a material comprising at least a low polymer organic semiconductor compound for example, an oligothiophene derivative as shown in FIG. 16 which has a smectic liquid crystalline phase at a high temperature.
  • the organic semiconductor compound having a liquid crystal phase of a high order at a high temperature means that a crystallization temperature at which crystallization occurs from at least the liquid crystalline phase of a high order is not lower than room temperature and the liquid crystalline phase of a high order is exhibited at a temperature within a temperature range that is higher than the crystallization temperature.
  • the oligothiophene derivative shown in FIG. 16 is an organic semiconductor compound comprising Dec-5T-Dec (wherein Dec represents an alkyl group having 10 carbon atoms) including five thiophene rings T bonded to each other as inverted every other ring.
  • Dec-5T-Dec wherein Dec represents an alkyl group having 10 carbon atoms
  • DSC differential scanning thermal analysis
  • An organic compound material to be mixed with the oligothiophene derivative as the aforementioned organic semiconductor compound is a liquid crystal compound prepared by mixing of organic compounds each exhibiting at least the second liquid crystalline phase like a nematic phase of a low order (i.e., a liquid crystalline phase of high low symmetry), for example, cyanobiphenyl-type compounds as shown in FIGs. 17(a) and 17(b) or cyanoterphenyl-type compounds as shown in FIG. 17(c) (hereinafter will be generally referred to as biphenyl-type compounds).
  • R and Ra are each a straight- or branched-chain alkyl group having at least 3 to 8 carbon atoms.
  • Such biphenyl-type liquid crystal compounds form a nematic liquid crystal compound comprising plural components in which R and Ra are different.
  • a mixed nematic liquid crystal compound prepared by mixing a liquid crystal compound of another type with such a nematic liquid crystal compound may be used. It is also possible to use a nematic liquid crystal compound not substituted with a cyano or fluoro group.
  • the temperature range within which the organic compound exhibits a nematic liquid crystalline phase may be lower or higher than the temperature range within which the organic semiconductor compound exhibits a smectic phase.
  • FIG. 13 is a conceptual diagram showing an exemplary phase diagram of a mixed composition comprising an organic semiconductor compound and an organic compound according to the present embodiment.
  • the abscissa represents the weight (%) of the oligothiophene derivative and the weight of the biphenyl liquid crystal compound increases with decreasing weight of the oligothiophene derivative.
  • the ordinate in FIG. 13 represents the phase transition temperature (°C).
  • the oligothiophene derivative Dec-5T-Dec as the organic semiconductor compound has a smectic phase (S) at a temperature within the range from 100°C to 170°C and turns into an isotropic liquid (I) at a temperature not lower than 170°C.
  • S smectic phase
  • I isotropic liquid
  • a mixed composition prepared by mixing 93 wt% of the oligothiophene derivative Dec-5T-Dec as the organic semiconductor compound and 7 wt% of the biphenyl-type liquid crystal compound exhibits a nematic phase (N) within the temperature range from 160°C to 167°C.
  • a mixed composition comprising a mixture of at least 93 wt% of the organic semiconductor compound having the first liquid crystalline phase of a high order at a high temperature or of a potentially high order and 7 wt% of the organic compound exhibiting the second liquid crystalline phase of a low order like a nematic phase.
  • the above-described mixed composition may be blended with an organic solvent such as chlorobenzene for easy coating.
  • the mixed composition preferably contains the organic semiconductor compound in a highest possible proportion, so that desired high characteristics can be obtained easily.
  • the mixed composition desirably contains 70 to 98 wt% of the organic semiconductor compound, more desirably 90 to 95 wt% of the organic semiconductor compound. Such a mixed composition can obtain much higher characteristics.
  • the present invention is not limited to the above-noted mixture ratios.
  • At least two electrodes 3 and 4 are disposed opposite to each other on a substrate 2 such as a glass substrate or a plastic substrate, as shown in FIG. 12(a) .
  • a polyimide film is formed to a thickness of 100 nm by spin coating and then baked to form an orientation film (not shown) for orienting the second liquid crystal phase to be exhibited. Thereafter, at least a portion of the orientation film which extends over the electrodes 3 and 4 is subjected to an orientation treatment.
  • the method of orientation treatment employed here includes rubbing the surface of the orientation film with dust-free cloth in a desired fixed direction, for example, in the direction from the electrode 3 toward the electrode 4 (indicated by arrow) like the method employed in the liquid crystal display technology to orient a liquid crystal material injected between opposite substrates.
  • a solution of the aforementioned mixed composition is dropped to an orientation-treated region extending over the electrodes 3 and 4 on the substrate 2 from a dropping nozzle 32 by a dropping method to form a film having a thickness of about 1 ⁇ m, as shown in FIG. 12(b) .
  • at least a solution portion of the mixed composition is heated to dissipate the organic solvent from the solution of the mixed composition, thus forming a mixed composition layer 33.
  • the mixed composition layer 33 coating at least the space between the electrodes 3 and 4 is left within a predetermined temperature range, as shown in FIG. 12(c) .
  • the "predetermined temperature range”, as used here, is meant by a temperature range that allows the mixed composition to exhibit a nematic phase as the second liquid crystalline phase of a low order containing the oligothiophene derivative shown in FIG. 16 .
  • the mixed composition layer 33 comprising the mixture of 93 wt% of the organic semiconductor compound and 7 wt% of the organic compound as exemplified in the present embodiment exhibited nematic phase 34 oriented in a desired direction as the second liquid crystalline phase of a low order over the electrodes 3 and 4 within the temperature range from 160°C to 167°C in conformance with the phase diagram at FIG. 13 .
  • the nematic phase 34 exhibited in at least the space between the electrodes 3 and 4 and the boundaries thereof is gradually cooled and solidified to form the conductive thin film 35 comprising the mixed composition layer 33 containing 93 wt% of the organic semiconductor compound and oriented in the predetermined direction.
  • the nematic phase 34 it is possible to form a solid phase maintaining the composition of mixture and orientation of the nematic phase 34 by gradually cooling and solidifying the namatic phase 34.
  • the skeletal chains of the oligothiophene derivative which is mixed with the biphenyl-type liquid crystal compound and in which thiophene rings are bonded to each other are aligned in the predetermined fixed direction, for example, in the direction from the electrode 3 toward the electrode 4, relative to the molecules of the biphenyl-type liquid crystal compound oriented in the desired fixed direction by the orientation treatment. Accordingly, by adjusting the alignment direction of the organic compound mixed which exhibits the nematic phase to the predetermined direction by means of the aforementioned orientation treatment, it is possible to adjust alignment direction of the skeletal chains of the organic semiconductor compound to the predetermined direction.
  • the predetermined direction in which the organic compound is oriented by the orientation treatment and the predetermined direction in which the skeletal chains of the organic semiconductor compound are aligned due to the orientation of the organic compound may be the same or different. That is, the indispensable feature of the present invention is that the organic semiconductor compound is aligned in the predetermined direction.
  • the conductive thin film 35 formed according to the present embodiment exhibited a high carrier mobility as high as 10 -2 cm 2 /Vs. Thus, it was confirmed that the characteristics of the conductive thin film in which the oligothiophene derivative was oriented in the substantially fixed predetermined direction were improved. In contrast, a conductive thin film formed using the same oligothiophene derivative as used in the present embodiment by vapor deposition exhibited is a low carrier mobility as low as 10 -3 cm 2 /Vs.
  • the conductive thin film was further improved in carrier mobility and electric conductivity which was formed by the process including: using the mixed composition layer comprising a mixture of the organic semiconductor compound having the first liquid crystalline phase of a high order at a high temperature and the organic compound exhibiting the second liquid crystalline phase of a low order; leaving the mixed composition layer within the predetermined temperature range to allow the mixed composition layer to exhibit the second liquid crystalline phase of a low order containing the organic semiconductor compound between the electrodes formed on the substrate; and causing the second liquid crystalline phase to be oriented in the predetermined direction, thereby also orienting the molecules of the organic semiconductor compound in the predetermined direction.
  • the first liquid crystalline phase is a smectic phase and the second liquid crystalline phase is a nematic phase.
  • the organic semiconductor compound comprises such a low polymer organic semiconductor compound as the oligothiophene derivative. By orienting the low polymer organic semiconductor compound substantially uniformly, the conductive thin film containing the low polymer organic semiconductor compound can be improved in such electrical characteristics as carrier mobility and electric conductivity.
  • the oligothiophene derivative as the organic semiconductor compound is a derivative comprising plural thiophene rings bonded to each other. Since such an oligothiophene derivative comprising at least 4 to 6 thiophene rings bonded to each other has a smectic phase under a high temperature condition, the present invention can use such oligothiophene derivatives.
  • FIG. 14 is a sectional view schematically showing the construction of a thin film transistor according to embodiment 7 of the present invention.
  • the thin film transistor 37 shown in FIG. 14 includes a gate electrode 17 of a desired shape formed on an insulating substrate 2, and a semiconductor layer 36 forming a channel layer and formed above the gate electrode 17 with an intervening gate insulator 9 therebetween. Also, source electrode 11 and drain electrode 12 are formed between the insulating substrate 2 and the semiconductor layer 36 so as to connect directly to the semiconductor layer 36. Usually, a cap layer is stacked over the gate electrode 17, source and drain electrodes 11 and 12 and semiconductor layer 36. Further, lead electrodes, which are not shown for avoiding complicated illustration, are connected to respective of the source and drain electrodes 11 and 12.
  • FIG. 15 is a sectional view schematically illustrating a process for fabricating the thin film transistor according to embodiment 7 of the present invention.
  • some conventional parts or components required in fabricating the thin film transistor are omitted for avoiding complicated illustration.
  • an aluminum film is formed to a thickness of 300 nm on a surface of the insulating substrate 2 comprising a plastic substrate or a glass substrate, followed by photolithography and etching to form the gate electrode 17.
  • a polyimide film having a thickness of 100 nm is formed to cover the gate electrode 17 and the exposed portion of the substrate 2 by spin coating, to form the gate insulator 9.
  • an indium tin oxide film (ITO) as a conductive thin film is formed to a thickness of 300 nm on the upper side of the gate insulator 9 by EB evaporation at a substrate temperature of 100°C.
  • the indium tin oxide film is then subjected to photolithography and etching to form the source and drain electrodes 11 and 12.
  • at least a portion of the gate insulator 9 lying between the source and drain electrodes 11 and 12 is subjected to an orientation treatment.
  • the method of orientation treatment employed here includes rubbing the surface of the gate insulator 9 with dust-free cloth in a predetermined direction, like the method employed in embodiment 6.
  • Such an orientation treatment allows a liquid crystalline organic compound contained in a mixed composition layer, which is to be described later, to be oriented in a direction parallel with the rubbing direction.
  • the surface of the gate insulator 9 is subjected to the orientation treatment after the formation of the source and drain electrodes 11 and 12 according to the above-described embodiment, there is no limitation to this embodiment.
  • the semiconductor layer 36 comprising an organic semiconductor film is formed on the upper side of the gate insulator 9 to serve as a channel layer, as shown in FIG. 14 .
  • the semiconductor layer 36 is formed in the following manner as in the formation of the conductive thin film of embodiment 6.
  • a material comprising at least such a low polymer organic semiconductor compound as the oligothiophene derivative having a smectic phase as a liquid crystalline phase of a high order at a high temperature, for example, Dec-5T-Dec shown in FIG. 16 .
  • a material comprising at least 4 to 6 thiophene rings bonded to each other as the thiophene derivative.
  • an organic compound which exhibits the second liquid crystalline phase like a nematic phase of a low order i.e., a liquid crystalline phase of low symmetry
  • a biphenyl-type compound shown in FIG. 17(a) a mixed composition is prepared by mixing at least 93 wt% of the oligothiophene derivative Dec-5T-Dec as the organic semiconductor compound and 7 wt% of the biphenyl-type liquid crystal compound as the organic compound together.
  • the mixed composition is then blended with an organic solvent such as chlorobenzene for easy coating.
  • a solution of the aforementioned mixed composition thus prepared is coated to the exposed portion of the polyimide gate insulator 9 having a surface orientation-treated by rubbing in the predetermined direction and to the upper side of the source and drain electrodes 11 and 12 by a dropping method to form a film having a thickness of about 1 ⁇ m, as shown in FIG. 15(b) .
  • at least a solution portion of the mixed composition is heated to dissipate the organic solvent from the solution of the mixed composition, thus forming a mixed composition layer 38 containing 93 wt% of the oligothiophene derivative as the organic semiconductor compound.
  • the mixed composition layer preferably contains the organic semiconductor compound in a highest possible proportion, so that desired high characteristics can be obtained easily.
  • the mixed composition layer 38 desirably contains 70 to 98 wt% of the organic semiconductor compound, more desirably 90 to 95 wt% of the organic semiconductor compound. Such a mixed composition layer can obtain more favorable characteristics.
  • the mixture ratio of the organic semiconductor compound in the mixed composition layer 38 is not limited to the above-noted mixture ratios but may be appropriately adjusted to the kind of the organic semiconductor compound or the required electrical characteristics.
  • the mixed composition layer 38 coating at least the space between the source and drain electrodes 11 and 12 is left within a predetermined temperature range that allows the mixed composition to exhibit a nematic phase as the second liquid crystalline phase of a low order containing the oligothiophene derivative shown in FIG. 16 .
  • the mixed composition 38 comprising the mixture of the organic semiconductor compound Dec-5T-Dec (93 wt%) and the organic compound (7 wt%) exhibits nematic phase 39 within the temperature range from 160°C to 167°C in conformance with the phase diagram at FIG. 13 .
  • the nematic phase 39 exhibited in at least the space between the source and drain electrodes 11 and 12 and the boundaries thereof is gradually cooled and solidified to form the semiconductor layer 36 as an organic semiconductor layer comprising the mixed composition layer 38 containing 93 wt% of the organic semiconductor compound and oriented in the predetermined direction.
  • the semiconductor layer 36 of the thin film transistor 37 shown in FIG. 14 is completed.
  • molecules of the oligothiophene derivative as the organic semiconductor compound mixed with the biphenyl-type compound are aligned in the substantially fixed predetermined direction (for example, in the direction from the source electrode 11 toward the drain electrode 12) relative to the biphenyl-type liquid crystal compound oriented in the desired fixed direction by the orientation treatment.
  • the thin film transistor 37 having the semiconductor layer 36 as the organic semiconductor layer formed according to the present embodiment exhibited a high carrier mobility at channel as high as 10 -2 cm 2 /Vs.
  • the semiconductor layer 36 containing the oligothiophene derivative oriented in the substantially fixed predetermined direction was improved in electrical characteristics.
  • a thin film transistor having a semiconductor layer formed using the same oligothiophene derivative as used in the present embodiment by mere vapor deposition exhibited a low carrier mobility as low as 10 -3 cm 2 /Vs.
  • the mixed composition layer is formed by coating the space between the source and drain electrodes formed on the substrate with the mixed composition comprising a mixture of the organic semiconductor compound having the first liquid crystalline phase of a high order at a high temperature and the organic compound exhibiting the second liquid crystalline phase of a low order and then left within the predetermined temperature range that allows the mixed composition layer to exhibit the second liquid crystalline phase of a low order containing the organic semiconductor compound. Thereafter, the mixed composition layer lying between the source and drain electrodes is allowed to exhibit the second liquid crystalline phase, which is then oriented in the desired direction. By so doing, the molecules of the organic semiconductor compound also are oriented in the predetermined direction. In this way, the conductive thin film is formed which is enhanced in charge transport performance by favorably orienting the molecules of the organic semiconductor compound. By utilizing this conductive thin film as a semiconductor layer, the thin film transistor having further improved carrier mobility at channel is fabricated.
  • the first liquid crystalline phase is a smectic phase and the second liquid crystalline phase is a nematic phase.
  • the semiconductor layer can be formed easily.
  • the organic semiconductor compound comprises a low polymer of an organic semiconductor compound such as the oligothiophene derivative. If a conductive thin film is formed in which such a low polymer of the organic semiconductor compound is oriented substantially uniformly, use of such a conductive thin film as the semiconductor layer in a thin film transistor will make it possible to improve the thin film transistor in such electrical characteristics as carrier mobility at channel.
  • the above-described temperature at which the organic compound exhibits a nematic liquid crystalline phase may be lower or higher than the temperature at which the organic semiconductor compound exhibits a smectic phase.
  • oligothiophene derivative used as the organic semiconductor compound may be any oligothiophene derivative which exhibits a smectic phase with no limitation on the number of thiophene rings or the length of the alkyl group.
  • the present invention is not limited to this embodiment but can be practiced similarly with use of any one of materials which are each capable of exhibiting a smectic phase, including derivatives of such low polymer organic semiconductor compounds as pentacene, tetracene, phenylene derivative, phthalocyanine compound, cyanine dye, and the like.
  • nematic liquid crystal compounds each having a substantially rod-like molecular structure such as phenylcyclohexane (PCH)-type, phenyl ester-type, phenylpyrimidine-type, phenyldioxane-type, and tolan-type nematic liquid crystal compounds, nematic liquid crystal compounds of other types, and mixed nematic liquid crystal compounds each comprising a mixture thereof.
  • PCH phenylcyclohexane
  • phenyl ester-type phenylpyrimidine-type
  • phenyldioxane-type phenyldioxane-type
  • tolan-type nematic liquid crystal compounds nematic liquid crystal compounds of other types
  • mixed nematic liquid crystal compounds each comprising a mixture thereof.
  • the present invention is not limited to this embodiment but may use a lyotropic liquid crystal.
  • the organic semiconductor compound may be oriented by utilizing an electric field generated by application of voltage across the source and drain electrodes instead of the above-described orientation film having undergone the orientation treatment.
  • the above-described mixed composition can serve the purpose as long as the mixed composition comprises at least the aforementioned organic semiconductor compound and the aforementioned organic compound.
  • the mixed composition may contain other materials such as a charge polarity imparting agent.
  • the kind of the organic solvent described above may be appropriately selected depending upon the kind of the organic semiconductor compound selected.
  • an aromatic solvent such as chloroform, 1,2,4-trichlorobenzene or the like, as well as chlorobenzene mentioned above.
  • an organic solvent such as tetrahydrofuran, diethyl glycol, diethyl ether or the like.
  • Methods of coating of the above-described mixed composition include casting, spinner coating, dip coating, such printing as screen printing, roll coating, ink-jet coating, spray coating, and a like method, in addition to the aforementioned dropping.
  • Methods of orienting the above-described liquid crystalline phase in any predetermined direction include: a method including applying the organic semiconductor film with an electric field; a method including applying the organic semiconductor film with a magnetic field; and a like method, in addition to the above-described method including forming the organic semiconductor film on the orientation film having undergone the orientation treatment.
  • the present invention is not limited to this embodiment but may utilize a composite-type semiconductor layer formed from a mixed composition comprising a composite-type semiconductor material composed of an organic semiconductor compound and semiconductive carbon nanotube, and a liquid crystalline organic compound.
  • the above-described thin film transistor according to the present embodiment comprises the gate insulator, the semiconductor layer disposed in contact with the gate insulator, the gate electrode disposed in contact with one side of the gate insulator on the side opposite away from the semiconductor layer, and the source and drain electrodes disposed in contact with at least one side of the semiconductor layer and aligned with the gate electrode so as to be opposed to each other across the gate electrode.
  • the thin film transistor according to the present invention has been described as a bottom-gated thin film transistor having the gate electrode on the substrate, or on the bottom, the thin film transistor of the present invention may be a top-gated thin film transistor having the gate electrode on the gate insulator on the side opposite away from the substrate, or on the top.
  • the material usable for the gate electrode 17 and the source and drain electrodes 11 and 12 may be any material which is electrically conductive and unreactive to any one of the substrate 2 and the semiconductor layer 36.
  • examples of such usable materials include doped silicon, precious metals such as gold, silver, platinum and palladium, alkali metals or alkali earth metals such as lithium, cesium, calcium and magnesium, and metals such as copper, nickel, aluminum, titanium and molybdenum, or alloys thereof.
  • Other usable materials include conductive organic materials such as polypyrrole, polythiophene, polyaniline and polyphenylenevinylene. Since the thin film transistor is operable if the gate electrode has a higher electric resistance than other electrodes, the gate electrode in particular may comprise a material different from that of the source and drain electrodes.
  • the material usable for the aforementioned gate insulator 9 may be any material which has an electric insulating property and is unreactive to any one of the substrate 2, electrodes and semiconductor layer 36.
  • the substrate 2 and the gate insulator 9 may be in a form wherein a typical silicon oxide film is formed on silicon so as to be used as the gate insulator, or in a form wherein a thin layer of resin or the like is formed after the formation of an oxide film so as to function as the gate insulator.
  • the gate insulator 9 may be formed by deposition of a compound consisting of elements different from those forming the substrate 2 and from those forming the electrodes by means of CVD, vapor deposition, sputtering or the like, or by coating, spraying, electrodeposition or the like of a solution of such a compound. Since it is known that a material having a high dielectric constant is used as the material for the gate insulator 9 in order to lower the gate voltage of the thin film transistor 37, the gate insulator 9 may be formed using a compound having a high dielectric constant other than ferroelectric compounds and ferroelectrics. Besides inorganic materials, it is possible to use organic materials having high dielectric constants such as polyvinylidene fluoride compounds, polyvinylidene cyanide compounds and the like.
  • the present embodiment can use the conventional low-temperature thin film formation technology in the formation of a thin film or a semiconductor layer, it is possible to use, besides a flexible plastic sheet that can be bent and a thin glass substrate, a resin film substrate having suppleness such as a thin polyimide film as the aforementioned substrate 2.
  • a resin film substrate having suppleness such as a thin polyimide film as the aforementioned substrate 2.
  • polyethylene film, polystyrene film, polyester film, polycarbonate film, polyimide film and a like film Such a film also can provide for a flexible paper display, sheet display or the like having a substrate comprising a plastic sheet or a resin film.
  • the conductive thin film, thin film transistor and method of fabricating them according to the present invention are useful as conductive thin film, thin film transistor and method of fabricating them in realizing microminiaturized and higher-performance semiconductor circuits and display devices. Also, the conductive thin film, thin film transistor and method of fabricating them are useful as conductive thin film, thin film transistor and method of fabricating them in realizing paper-like or sheet-shaped image display devices, mobile devices using small-sized and high-performance semiconductor circuit devices, disposable devices such as a wireless IC tag, or other electronic devices, robots, microminiaturized medical instruments, or the like. Further, the conductive thin film, thin film transistor and method of fabricating them are useful as conductive thin film, thin film transistor and method of fabricating them in fabricating such a semiconductor circuit device, display device or the like inexpensively.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Nanotechnology (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Mathematical Physics (AREA)
  • Theoretical Computer Science (AREA)
  • Thin Film Transistor (AREA)

Claims (14)

  1. Leitender Dünnfilm (1), gebildet durch Zusammenmischen von wenigstens Nanoröhrchen, umfassend wenigstens eines von metallischen Nanoröhrchen und halbleitenden Nanoröhrchen, und eine flüssigkristalline organische Verbindung (6) mit einer Ladungstransportfunktion, und Ausrichten von Molekülen der flüssigkristallinen organischen Verbindung (6), um zu bewirken, dass Moleküle der Nanoröhrchen ausgerichtet werden.
  2. Leitender Dünnfilm (1) gemäß Anspruch 1, wobei die Nanoröhrchen Kohlenstoff-Nanoröhrchen (5) sind.
  3. Leitender Dünnfilm (1) gemäß Anspruch 1 oder Anspruch 2, wobei die flüssigkristalline organische Verbindung (6) eine flüssigkristalline organische Verbindung mit wenigstens einem von einer nematischen flüssigkristallinen Phase und einer smektischen flüssigkristallinen Phase ist.
  4. Leitender Dünnfilm (1) gemäß Anspruch 1 oder Anspruch 2, wobei die flüssigkristalline organische Verbindung (6) eine flüssigkristalline organische Verbindung mit wenigstens 1 6-π-Elektronen-aromatischen Ringen, m 10-π-Elektronenaromatischen Ringen oder n 14-π-Elektronenaromatischen Ringen ist (wobei 1+m+n = 1 bis 4; und 1 und n jeweils eine ganze Zahl von 0 bis 4 sind).
  5. Leitender Dünnfilm (1) gemäß Anspruch 4, wobei die flüssigkristalline organische Verbindung (6) eine flüssigkristalline organische Verbindung mit wenigstens einem von einem 2-Phenylnaphthalinring, einem Biphenylring, einem Benzothiazolring und einem t-Thiophenring und einer im Wesentlichen stäbchenartigen Molekülstruktur ist.
  6. Verfahren zum Herstellen eines leitenden Dünnfilms (1), umfassend: Zusammenmischen von wenigstens Nanoröhrchen, umfassend wenigstens eines von metallischen Nanoröhrchen und halbleitenden Nanoröhrchen, und eine flüssigkristalline organische Verbindung (6) mit einer Ladungstransportfunktion; und Ausrichten von Molekülen der flüssigkristallinen organischen Verbindung, um zu bewirken, dass Moleküle der Nanoröhrchen ausgerichtet werden.
  7. Verfahren gemäß Anspruch 6, wobei Kohlenstoff-Nanoröhrchen (5) als die Nanoröhrchen verwendet werden.
  8. Verfahren gemäß Anspruch 6 oder Anspruch 7, wobei eine flüssigkristalline organische Verbindung mit wenigstens einem von einer nematischen flüssigkristallinen Phase und einer smektischen flüssigkristallinen Phase als die flüssigkristalline organische Verbindung (6) verwendet wird.
  9. Verfahren gemäß Anspruch 6 oder Anspruch 7, wobei eine flüssigkristalline organische Verbindung mit wenigstens 1 6-π-Elektronen-aromatischen Ringen, m 10-π-Elektronen-aromatischen Ringen oder n 14-π-Elektronen-aromatischen Ringen (wobei 1+m+n - 1 bis 4; und 1 und n jeweils eine ganze Zahl von 0 bis 4 sind) als die flüssigkristalline organische Verbindung (6) verwendet wird.
  10. Verfahren gemäß Anspruch 9, wobei eine flüssigkristalline organische Verbindung mit wenigstens einem von einem 2-Phenylnaphthalinring, einem Biphenylring, einem Benzothiazolring und einem t-Thiophenring und einer im Wesentlichen stäbchenartigen Molekülstruktur als die flüssigkristalline organische Verbindung (6) verwendet wird.
  11. Dünnfilmtransistor (30), umfassend einen leitenden Dünnfilm (1) gemäß einem der Ansprüche 1 bis 5 als Halbleiterschicht (31), die eine Kanalschicht bildet.
  12. Verfahren zum Herstellen eines Dünnfilmtransistors (30), umfassend ein Verfahren zum Herstellen eines leitenden Dünnfilms (1) gemäß einem der Ansprüche 6 bis 10 als Verfahren zum Herstellen eines leitenden Dünnfilms, der als Halbleiterschicht (31), die eine Kanalschicht bildet, dient.
  13. Bildanzeigeeinheit, umfassend einen leitenden Dünnfilm (1) gemäß einem der Ansprüche 1 bis 5 als wenigstens eines von einer leitenden Schicht und einer Halbleiterschicht, die eine Kanalschicht eines Dünnfilmtransistors (30) bildet.
  14. Elektronische Einheit, umfassend einen leitenden Dünnfilm (1) gemäß einem der Ansprüche 1 bis 5 als wenigstens eines von einer leitenden Schicht und einer Halbleiterschicht, die eine Kanalschicht eines Dünnfilmtransistors (30) bildet.
EP04793157A 2003-10-30 2004-10-28 Leitfähiger dünnfilm und dünnfilmtransistor Ceased EP1679752B1 (de)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP2003370384 2003-10-30
JP2003387885 2003-11-18
JP2003389104 2003-11-19
PCT/JP2004/016049 WO2005043639A1 (ja) 2003-10-30 2004-10-28 導電性薄膜および薄膜トランジスタ

Publications (3)

Publication Number Publication Date
EP1679752A1 EP1679752A1 (de) 2006-07-12
EP1679752A4 EP1679752A4 (de) 2009-11-11
EP1679752B1 true EP1679752B1 (de) 2011-11-30

Family

ID=34557009

Family Applications (1)

Application Number Title Priority Date Filing Date
EP04793157A Ceased EP1679752B1 (de) 2003-10-30 2004-10-28 Leitfähiger dünnfilm und dünnfilmtransistor

Country Status (5)

Country Link
US (1) US7746418B2 (de)
EP (1) EP1679752B1 (de)
JP (1) JP4878841B2 (de)
KR (1) KR100769788B1 (de)
WO (1) WO2005043639A1 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8946683B2 (en) 2008-06-16 2015-02-03 The Board Of Trustees Of The University Of Illinois Medium scale carbon nanotube thin film integrated circuits on flexible plastic substrates

Families Citing this family (42)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9422651B2 (en) * 2003-01-13 2016-08-23 Nantero Inc. Methods for arranging nanoscopic elements within networks, fabrics, and films
US8783577B2 (en) * 2005-03-15 2014-07-22 Semiconductor Energy Laboratory Co., Ltd. Semiconductor device and electronic device having the same
KR20060116534A (ko) * 2005-05-10 2006-11-15 삼성에스디아이 주식회사 박막 트랜지스터, 그 제조 방법 및 이를 구비한 평판 표시장치
JP5155153B2 (ja) * 2005-05-12 2013-02-27 メルク パテント ゲゼルシャフト ミット ベシュレンクテル ハフツング ポリアセンおよび半導体調製物
KR100647695B1 (ko) * 2005-05-27 2006-11-23 삼성에스디아이 주식회사 유기 박막 트랜지스터 및 그의 제조방법과 이를 구비한평판표시장치
JP4673135B2 (ja) * 2005-06-03 2011-04-20 大日本印刷株式会社 有機半導体層の形成方法
GB2428135B (en) * 2005-07-07 2010-04-21 Univ Surrey Improvements in thin film production
US7829474B2 (en) * 2005-07-29 2010-11-09 Lg. Display Co., Ltd. Method for arraying nano material and method for fabricating liquid crystal display device using the same
JP5157053B2 (ja) * 2005-08-26 2013-03-06 コニカミノルタホールディングス株式会社 有機半導体材料、有機半導体膜、有機半導体デバイス及び有機薄膜トランジスタ
WO2007026781A1 (ja) 2005-08-31 2007-03-08 Sumitomo Chemical Company, Limited トランジスタ及びその製造方法、並びに、このトランジスタを有する半導体装置
US7995777B2 (en) 2005-10-03 2011-08-09 Xun Yu Thin film transparent acoustic transducer
CN101400599B (zh) * 2006-03-10 2010-12-01 松下电器产业株式会社 各向异性形状部件的安装方法
US20070243658A1 (en) * 2006-04-14 2007-10-18 Katsura Hirai Production method of crystalline organic semiconductor thin film, organic semiconductor thin film, electronic device, and thin film transistor
US20070275498A1 (en) * 2006-05-26 2007-11-29 Paul Beecher Enhancing performance in ink-jet printed organic semiconductors
KR101206661B1 (ko) * 2006-06-02 2012-11-30 삼성전자주식회사 동일 계열의 소재로 형성된 반도체층 및 소스/드레인전극을 포함하는 유기 전자 소자
KR101304697B1 (ko) * 2006-06-07 2013-09-06 삼성전자주식회사 적층 유도 화합물을 사용한 유기 반도체 소재, 이를포함하는 조성물, 이를 이용한 유기 반도체 박막 및 유기전자 소자
KR100918362B1 (ko) * 2006-07-27 2009-09-22 주식회사 엘지화학 유기 박막 트랜지스터 및 이의 제조방법
CN100591613C (zh) * 2006-08-11 2010-02-24 清华大学 碳纳米管复合材料及其制造方法
KR101227144B1 (ko) 2006-12-13 2013-01-28 엘지디스플레이 주식회사 박막 트랜지스터 및 이의 제조 방법
CN101589482B (zh) 2007-01-26 2011-11-30 东丽株式会社 有机半导体复合材料、有机晶体管材料以及有机场效应晶体管
GB2450381B (en) * 2007-06-22 2009-11-11 Cambridge Display Tech Ltd Organic thin film transistors
JP5354570B2 (ja) * 2007-09-20 2013-11-27 独立行政法人産業技術総合研究所 縮合多環芳香族化合物薄膜の製造方法およびそれにより製造された縮合多環芳香族化合物薄膜
KR100951946B1 (ko) * 2007-11-30 2010-04-09 한양대학교 산학협력단 투명하고 플렉서블한 탄소나노튜브 박막 트랜지스터 및이의 제조방법
FR2925226A1 (fr) * 2007-12-12 2009-06-19 Commissariat Energie Atomique Transistor organique ayant des objets nanometriques de forme filaire dans une matrice organique semi-conductrice et procede de realisation
CN101515091B (zh) * 2008-02-22 2012-07-18 清华大学 液晶显示屏的制备方法
JP5292857B2 (ja) * 2008-03-03 2013-09-18 東レ株式会社 有機半導体コンポジット、有機トランジスタ材料ならびに有機電界効果型トランジスタ
EP2120274B1 (de) * 2008-05-14 2018-01-03 Tsing Hua University Dünnfilmtransistor auf Basis von Kohlenstoffnanoröhrchen
CN101599495B (zh) * 2008-06-04 2013-01-09 清华大学 薄膜晶体管面板
CN101587839B (zh) * 2008-05-23 2011-12-21 清华大学 薄膜晶体管的制备方法
GB2469507B (en) 2009-04-16 2011-05-04 Cambridge Display Tech Ltd Organic thin film transistors
US8841652B2 (en) 2009-11-30 2014-09-23 International Business Machines Corporation Self aligned carbide source/drain FET
US20110127492A1 (en) * 2009-11-30 2011-06-02 International Business Machines Corporation Field Effect Transistor Having Nanostructure Channel
EP2513952A1 (de) * 2009-12-17 2012-10-24 Merck Patent GmbH Abscheidung von nanopartikeln
US8348841B2 (en) * 2010-04-09 2013-01-08 The Board Of Trustees Of The University Of Arkansas Wireless nanotechnology based system for diagnosis of neurological and physiological disorders
JP5807738B2 (ja) * 2011-03-30 2015-11-10 ソニー株式会社 有機トランジスタの製造方法、有機トランジスタ、半導体装置の製造方法、半導体装置および電子機器
US8963131B2 (en) * 2011-06-13 2015-02-24 Samsung Electronics Co., Ltd. Electronic device
TWI508305B (zh) 2013-05-06 2015-11-11 E Ink Holdings Inc 主動元件
JP2014236148A (ja) * 2013-06-04 2014-12-15 東京エレクトロン株式会社 有機分子膜の形成装置および形成方法
WO2015061332A1 (en) * 2013-10-23 2015-04-30 Heilux, Llc High powered led light module with a balanced matrix circuit
TWI667795B (zh) 2014-09-25 2019-08-01 日商富士軟片股份有限公司 有機場效電晶體、有機半導體結晶的製造方法及有機半導體元件
US10217819B2 (en) * 2015-05-20 2019-02-26 Samsung Electronics Co., Ltd. Semiconductor device including metal-2 dimensional material-semiconductor contact
JP6350757B2 (ja) 2016-06-06 2018-07-04 東レ株式会社 メモリアレイ、メモリアレイの製造方法、メモリアレイシート、メモリアレイシートの製造方法および無線通信装置

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0983040A (ja) 1995-09-12 1997-03-28 Sharp Corp 薄膜トランジスタ及びその製造方法
US6326640B1 (en) * 1996-01-29 2001-12-04 Motorola, Inc. Organic thin film transistor with enhanced carrier mobility
TW410478B (en) 1998-05-29 2000-11-01 Lucent Technologies Inc Thin-film transistor monolithically integrated with an organic light-emitting diode
JP2001354966A (ja) * 2000-06-12 2001-12-25 Dainippon Ink & Chem Inc 混合液晶材料およびこれを用いた有機フォトリフラクティブ素子
JP2002365427A (ja) 2001-06-04 2002-12-18 Toray Ind Inc 偏光子およびその製造方法
ATE303389T1 (de) * 2001-07-09 2005-09-15 Merck Patent Gmbh Thienothiophen-derivate
JP2003258261A (ja) * 2002-02-28 2003-09-12 Nippon Hoso Kyokai <Nhk> 有機ｔｆｔおよびその作製方法

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8946683B2 (en) 2008-06-16 2015-02-03 The Board Of Trustees Of The University Of Illinois Medium scale carbon nanotube thin film integrated circuits on flexible plastic substrates

Also Published As

Publication number Publication date
EP1679752A4 (de) 2009-11-11
US7746418B2 (en) 2010-06-29
EP1679752A1 (de) 2006-07-12
KR100769788B1 (ko) 2007-10-25
US20080277648A1 (en) 2008-11-13
JP4878841B2 (ja) 2012-02-15
KR20060080238A (ko) 2006-07-07
JPWO2005043639A1 (ja) 2008-06-12
WO2005043639A1 (ja) 2005-05-12

Similar Documents

Publication Publication Date Title
EP1679752B1 (de) Leitfähiger dünnfilm und dünnfilmtransistor
KR100600687B1 (ko) 트랜지스터 및 그 트랜지스터를 포함하는 디스플레이 장치
CN100420032C (zh) 场效应晶体管及其制造方法
JP4194436B2 (ja) 電界効果型有機トランジスタ
JP5615347B2 (ja) 有機薄膜トランジスタの製造方法
TW201330343A (zh) 製造有機半導體元件之方法、半導體元件及電子裝置
JP4139096B2 (ja) トランジスタ及びそれを用いた表示装置
JP4419425B2 (ja) 有機薄膜トランジスタ素子
CN100592545C (zh) 导电性薄膜和薄膜晶体管
JP4408030B2 (ja) トランジスタ、表示装置、トランジスタの製造方法、および、表示装置の製造方法
WO2005006449A1 (ja) 有機薄膜トランジスタとその製造方法、及びそれを用いたアクティブマトリクス型のディスプレイと無線識別タグ
JP2005072200A (ja) 電界効果型有機トランジスタ
JP2004273514A (ja) 有機薄膜トランジスタおよびその製造方法
JP5630364B2 (ja) 有機半導体素子の製造方法および有機半導体素子
JP2008140883A (ja) 有機薄膜トランジスタ
JP2008147225A (ja) 有機薄膜トランジスタの製造方法、及び該製造方法により製造した有機薄膜トランジスタ
JP2015159169A (ja) 電極修飾用組成物、電極修飾方法および有機薄膜トランジスタ
JP2008098485A (ja) 有機半導体トランジスタ素子及びその製造方法、並びに半導体装置及び表示素子
JP5310567B2 (ja) 薄膜トランジスタ及びその製造方法
JP2004247558A (ja) 有機薄膜トランジスタ素子
JP2004273512A (ja) 有機薄膜トランジスタおよびその製造方法
JP2005322787A (ja) 有機薄膜トランジスタ
JP2004273513A (ja) 有機薄膜トランジスタおよびその製造方法
JP2006049775A (ja) 電界効果型有機トランジスタ及びその製造方法
JP2006049776A (ja) 電界効果型有機トランジスタ

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 20060522

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): DE GB NL

DAX Request for extension of the european patent (deleted)
RBV Designated contracting states (corrected)

Designated state(s): DE GB NL

RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: PANASONIC CORPORATION

A4 Supplementary search report drawn up and despatched

Effective date: 20090908

17Q First examination report despatched

Effective date: 20091222

GRAP Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOSNIGR1

GRAS Grant fee paid

Free format text: ORIGINAL CODE: EPIDOSNIGR3

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): DE GB NL

REG Reference to a national code

Ref country code: GB

Ref legal event code: FG4D

REG Reference to a national code

Ref country code: DE

Ref legal event code: R096

Ref document number: 602004035558

Country of ref document: DE

Effective date: 20120126

REG Reference to a national code

Ref country code: NL

Ref legal event code: T3

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed

Effective date: 20120831

REG Reference to a national code

Ref country code: DE

Ref legal event code: R097

Ref document number: 602004035558

Country of ref document: DE

Effective date: 20120831

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 20121028

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20121028

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 20200915

Year of fee payment: 17

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 20201022

Year of fee payment: 17

REG Reference to a national code

Ref country code: DE

Ref legal event code: R119

Ref document number: 602004035558

Country of ref document: DE

REG Reference to a national code

Ref country code: NL

Ref legal event code: MM

Effective date: 20211101

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20211101

Ref country code: DE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20220503